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Post by 90GTVert on Jun 17, 2024 7:25:55 GMT -5
Have you investegated how Euro racing scooters are setup intake wise? I looked at what I could find of scoots in the Malossi racing series using RC1s at your suggestion long ago when I was having issues with the bowl draining in the VHST. My issue turned out to be fuel supply then, but it looked like they were just doing what I am and using whatever angle intake rubber rotation gave them. I think the one I use puts the carb at less angle than what the other RC1s I’ve been around use. |
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Post by billwill on Jun 17, 2024 7:40:17 GMT -5
Well you shouldn't be able to hold you cylinder after riding your scoot since the coolant alone should be at least 50°c As far gasoline you can even use 81 if you like to just need to adjust compression ratio and squish. Again I don't know how you have your engine setup but for example you can have too much compression and the squish can be too low that will cause problems like the one you have right now. As I seen on those cases the intake it's awfully wrong with a stupid inclin foward leaving the carb way of. I would suggest to create a spacer to tilt the carb more Retad the ignition more and start tuning from there. If you can't make the spacer let me know I can help with that since I have a milling machine. I don't know that I can always hold the cylinder, but I can touch it and it's not burning me. Maybe not the smartest to go grabbing stuff, but real world I think a lot of us have touched enough coolant hose, heads, etc... to have some idea if it's way off. From what attention I do pay to CHT, it doesn't look way off either. The abnormal heat appears to be in the exhaust. The head is not modified from original. Squish is essentially to spec. Was 0.54mm last time with 0.55-0.6 as Malossi's spec, but with the gaskets 0.54 was the best I could do. It was either that or go more above 0.6 (forget the exact other option now), but I'd rather be 0.01 tighter. 0.54 is 1.23%, 0.55 would be 1.25% and I'd have to go to 0.44 to be at 1%. 0.01 should be insignificant and I've used 0.55 and larger with the same results on past assemblies. I'm curious what the advantage is of a carb sitting upright if the fuel level is known to work. John has suggested putting another pipe in the intake to level the carb, but I thought it was to be sure fuel supply was correct. I guess the difference in gravity could have some effect on how fuel is drawn up, but if anything wouldn't the angle actually make it easier for fuel to get up into the intake path vs having to go straight up? No one should manufacturer tilted bowl carbs if the tilted carb throws everything off. Thanks. I've said it before I think, but for anyone offering ideas or suggestions please don't take my comments as arguing. I'm thinking along and hoping that maybe for all of the expense and effort I will learn along the way. I'd rather question anyone than follow blindly with no understanding of why it's supposed to work. As happy as I'd be if this thing stopped trying to eat pistons, I'd be a bit sad if it quit and I didn't have a good idea of why. I have another person with an interesting theory about flow that makes sense, but they are PM-ing me so I want to make sure it's OK if I quote them here before I post their thoughts. Like you, here in the states (even in the same state as you), it's hard to get anything above 91/93 pump gas without spending an arm and a leg. I went through an issue with pinging/knock a while back with my bike when squish was set to .55mm. I tried using c12 and that cooled things down a bit and completely got rid of the detonation, but it didn't cool them down enough. I had to reset squish to be a little higher and set it to .68/.69mm and that helped even more but it still runs hot even with retarding the timing so I might increase it even more to .75/.8mm. When researching things, I came across a forum post on a two-stroke MX forum where they were talking about octane and residual fuel left in fuel lines from shared use of pumps for multiple octane fuels. When filling up small tanks of gas for 1-2 gallons for premix, be sure to throw a gallon or two of premium in your vehicle BEFORE filling your can. There is a small amount of fuel left in the pump line from the person that used it before you. And if they had used a lower octane fuel, then you are getting some of that too when you begin filling. I tested this when my motor was knocking - using this method and not, and I when I used it, it went away. I guess if you're filling a 20 gallon tank, the residual fuel is negligible, but when filling a gallon can, it can have an effect. It might be interesting to try race fuel too just to see if that cools things down for you. I know this might not have much of an effect on EGTs (probably would more with CHTs), and if you're anything like me don't want to be paying $20/gal for fuel, but it could provide you some more data to make your next move(s). Maybe there are some small airports out your way where you can get it cheaper than having to pay for a pail of VP c12 or something. Have you investegated how Euro racing scooters are setup intake wise? I looked at what I could find of scoots in the Malossi racing series using RC1s at your suggestion long ago when I was having issues with the bowl draining in the VHST. My issue turned out to be fuel supply then, but it looked like they were just doing what I am and using whatever angle intake rubber rotation gave them. I think the one I use puts the carb at less angle than what the other RC1s I’ve been around use. From what I gather, and first-hand experience, the PWKs are more susceptible to odd behavior and issues as it pertains to their angle, at lower RPM, not high. On my MXS race scoot (mina vert - so the carb is facing left to right, not front to back), the idle can fluctuate and even stall the bike if I tip it to the left or right. It bugs me to not have a super crisp idle unless the bike is close to level, but apparently other guys have this issue too. |
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Post by xtremrox on Jun 17, 2024 10:04:39 GMT -5
I don't know that I can always hold the cylinder, but I can touch it and it's not burning me. Maybe not the smartest to go grabbing stuff, but real world I think a lot of us have touched enough coolant hose, heads, etc... to have some idea if it's way off. From what attention I do pay to CHT, it doesn't look way off either. The abnormal heat appears to be in the exhaust. The head is not modified from original. Squish is essentially to spec. Was 0.54mm last time with 0.55-0.6 as Malossi's spec, but with the gaskets 0.54 was the best I could do. It was either that or go more above 0.6 (forget the exact other option now), but I'd rather be 0.01 tighter. 0.54 is 1.23%, 0.55 would be 1.25% and I'd have to go to 0.44 to be at 1%. 0.01 should be insignificant and I've used 0.55 and larger with the same results on past assemblies. I'm curious what the advantage is of a carb sitting upright if the fuel level is known to work. John has suggested putting another pipe in the intake to level the carb, but I thought it was to be sure fuel supply was correct. I guess the difference in gravity could have some effect on how fuel is drawn up, but if anything wouldn't the angle actually make it easier for fuel to get up into the intake path vs having to go straight up? No one should manufacturer tilted bowl carbs if the tilted carb throws everything off. Thanks. I've said it before I think, but for anyone offering ideas or suggestions please don't take my comments as arguing. I'm thinking along and hoping that maybe for all of the expense and effort I will learn along the way. I'd rather question anyone than follow blindly with no understanding of why it's supposed to work. As happy as I'd be if this thing stopped trying to eat pistons, I'd be a bit sad if it quit and I didn't have a good idea of why. I have another person with an interesting theory about flow that makes sense, but they are PM-ing me so I want to make sure it's OK if I quote them here before I post their thoughts. Like you, here in the states (even in the same state as you), it's hard to get anything above 91/93 pump gas without spending an arm and a leg. I went through an issue with pinging/knock a while back with my bike when squish was set to .55mm. I tried using c12 and that cooled things down a bit and completely got rid of the detonation, but it didn't cool them down enough. I had to reset squish to be a little higher and set it to .68/.69mm and that helped even more but it still runs hot even with retarding the timing so I might increase it even more to .75/.8mm. When researching things, I came across a forum post on a two-stroke MX forum where they were talking about octane and residual fuel left in fuel lines from shared use of pumps for multiple octane fuels. When filling up small tanks of gas for 1-2 gallons for premix, be sure to throw a gallon or two of premium in your vehicle BEFORE filling your can. There is a small amount of fuel left in the pump line from the person that used it before you. And if they had used a lower octane fuel, then you are getting some of that too when you begin filling. I tested this when my motor was knocking - using this method and not, and I when I used it, it went away. I guess if you're filling a 20 gallon tank, the residual fuel is negligible, but when filling a gallon can, it can have an effect. It might be interesting to try race fuel too just to see if that cools things down for you. I know this might not have much of an effect on EGTs (probably would more with CHTs), and if you're anything like me don't want to be paying $20/gal for fuel, but it could provide you some more data to make your next move(s). Maybe there are some small airports out your way where you can get it cheaper than having to pay for a pail of VP c12 or something. I looked at what I could find of scoots in the Malossi racing series using RC1s at your suggestion long ago when I was having issues with the bowl draining in the VHST. My issue turned out to be fuel supply then, but it looked like they were just doing what I am and using whatever angle intake rubber rotation gave them. I think the one I use puts the carb at less angle than what the other RC1s I’ve been around use. From what I gather, and first-hand experience, the PWKs are more susceptible to odd behavior and issues as it pertains to their angle, at lower RPM, not high. On my MXS race scoot (mina vert - so the carb is facing left to right, not front to back), the idle can fluctuate and even stall the bike if I tip it to the left or right. It bugs me to not have a super crisp idle unless the bike is close to level, but apparently other guys have this issue too. The 2 most prominent problems with pwk are 1.the fuel flow being shit even on the keihins. Almost all of them flow like 2.8dl-3.5dl/min~max and it should be atleast 4.5dl/min 2.the float level being PIA to set and the flow problem makes this even worse as stock The way i have made even the chinese pwk work great is to drill the float needle valve/inlet valve hole, and set the fuel level high as possible rise it till it floods at idle when level and come down just a bit(there is ofeverflow ports for a reason) then tilting in turns/wheelies won't cause lean out and long pulls won't drain the bowl. Also to make the idle crisp and stable the ignition plays a big role i personally wont touch anything else than ignitech programmable cdi nowdays. You can make the curve from like 21 different points with basicly infinite adjustability. In my experience tuning ignition before a/f is spot on is risky as the optimal advance for power is 14-16°btdc at peak power and if the engine runs a bit lean its guaranteed to detonate. So first tune the carb then find out your peak power rpm and set the ignition so 14° btdc at that rpm. My usual ignition curve is something like 7-10° before idle rpm so the engine wont start backward accidentaly but is easy to start, then at idle i have 20-25 and immediatly like 200rpm from idle it changes to 30-35° depending on the engine and stays there until the power spike hits (usually 8-9krpm with these 50cc based high end engines) from there i grude tune it by setting the next point at peak power and 14° btdc and from there it drops to 7-9° at peak rpm to keep the pcp at reasonable °atdc and get good long power range. After that i test the power range charesteristics and rise the ignition between spike starting and peak power. Usually it needs only little adjusting |
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Post by xtremrox on Jun 17, 2024 10:15:19 GMT -5
Agreed, time to go back to the tried and trusted VHST Atleast in finland where i live and 2 stroke scooters and 50-300cc 2 strokes in general are the most popular 2 wheelers, EVERYONE uses pwk when going for power and ease of tune. And fr here we have THOUSANDS of highly tuned mopeds and 125cc bikes and a lot of 250-300cc too. The best carb sizes for 70-100cc have been found at 28-32mm (usually 28 does it only builds that i have seen a positive impact with larger are things like 96 bidalot ported 100cc 2fast ect) Yes from factory pwk has few flaws but they are super easy to fix and after that the pwk is absolytely the best carb for mortals. Before anyone says 28mm cant support power of +20hp just look at tuned sx85 ktms |
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Post by xtremrox on Jun 17, 2024 10:26:21 GMT -5
I don't think it's the exhaust I would not touch it! Why people love pwk simple it's just one of the best carbs in the world and very easy to work with. I keep telling you it's ignition related. I seen this problem sereval times during my 27 years as professional, For some reason ( keep in mind iam not seeing the engine) Your configuration is not working with that timing you should retard the ignition a decent amount and confirm readings once they 100% correct readings then tune the carb only after that you can start advancing the ignition. Why I say that let's exclude you might have odd problem on your engine/carb That ignition comes from Europe in Europe we have 95 98 and 100 oc fuel with very little content of ethanol Also the octane are measured ( Ron + Mon / 2) Our fuels in most countries in Europe will put any us fuel in a corner. When I came to us I had to build my engines at work differently from what I used to! So you could even just try your older ignition just 2 or 3 degrees retarded just to see your engine running. Also confirm those coolant Temps if possible check in and out Temps just to ensure proper cylinder dilatation. With the MVT that was on it, I had to advance it so I wasn't seeing 1300-1400 degree EGT. Current S6 ignition ran slightly cooler with 16 degree flat timing (about 20 degrees cooler EGT) than the MHR-ish curve. The MHR-ish curve that has advance at lower RPM should be 17* at 13,000RPM and falls to about 14* by 14,000, with 15.5* at 13,500 (roughly peak power). That happens to be the same range of timing that the MVT had when I saw EGT drop by advancing it, but the MVT had 45 degrees of advance out of the powerband... which seemed like a bad idea and is pretty much why I swapped since you can't change that much with any of the MVT curves (even if I had the EPROM). I don't want to argue with someone that has been there and tuned in Europe first hand, especially as a pro, but European octane ratings are typically RON vs our Anti-Knock Index (R+M)/2 so generally RON of 95-98 is said to be similar to our 91-93. I can get 94, which is basically equivalent to 100 RON rating, but I'd have to drive a good bit for 1 octane and overpay to boot. I can get ethanol free, but again overpaying and most sell it midgrade instead of premium locally for some reason and I don't really see the major benefit aside from when the scooter sits. I use 93 E10, pumped into a 5 gallon jug... usually 3-5 gallons at a time... so there's less contamination of lower octane since most pumps are single hose for 3 grades and many discussions have been had about how much fuel you get is actually whatever was previously selected vs what you choose. Plus, the two people that I've rode with using the MVT and MHR ignitions, both curves I've used now, are using premium pump gas (91-93 AKI) with the same engine and had no significant trouble dialing in their 34mm PWKs with smaller, more common, jetting. The one thing that does bug me is that I expect EGT to change with timing anyway, because you're moving more or less of the combustion heat into the pipe depending on advance. CHT really doesn't seem to reflect changes there much with the LC setup, especially the more effective ones (modular heads). I got wider, more useful, swings with AC engines monitoring CHT. Fancy stuff that you're more likely to see in a research lab would tell a more detailed story, but I don't think I'll be getting a research grant anytime soon. I have a wideband, but I can see the thick smoke rings and the bowl not running low, so I'd rather not put a bung in the exhaust and foul out my sensor. As far as the actual cylinder cooling, I can pull in from a ride and put my hand on the outer head or cylinder so it's definitely not way hot. Coolant temp reading (from the outer head) shows 120-140F mostly right now. Might start rising a little with it now getting into real summer heat, but not a lot. If squish and chamber desing are good you dont have to worry about octane rating that much. My friend had a husq sm125 with 15:1 comp 1% squish smth like 0.7mm if im correct and VERY radical ignition and made over 32whp on a dyno where x-cw ktm 125 made 27whp and no detonation on pump eu 98e5 octane and a747 oil at 4.5% The fact that your cylinder is that cool after riding is strange my 94cc italkit am6 was like 80-90C (like what 160-170°f?) When sending hard and no detonation and it had a big radiator directly at airflow and it had a high flow wp (not sure about your pump flow and cooling capacity of your radiator setup ect) but your temps seem low for some reason, it would kinda mach with the scenario i explaines in dm=poor cylinder filling and lower power=weaker detonation so no immediate melting on first pull and no central detonation and plug melting the piston |
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tysta
Scoot Member
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Post by tysta on Jun 17, 2024 10:47:05 GMT -5
With the MVT that was on it, I had to advance it so I wasn't seeing 1300-1400 degree EGT. Current S6 ignition ran slightly cooler with 16 degree flat timing (about 20 degrees cooler EGT) than the MHR-ish curve. The MHR-ish curve that has advance at lower RPM should be 17* at 13,000RPM and falls to about 14* by 14,000, with 15.5* at 13,500 (roughly peak power). That happens to be the same range of timing that the MVT had when I saw EGT drop by advancing it, but the MVT had 45 degrees of advance out of the powerband... which seemed like a bad idea and is pretty much why I swapped since you can't change that much with any of the MVT curves (even if I had the EPROM). I don't want to argue with someone that has been there and tuned in Europe first hand, especially as a pro, but European octane ratings are typically RON vs our Anti-Knock Index (R+M)/2 so generally RON of 95-98 is said to be similar to our 91-93. I can get 94, which is basically equivalent to 100 RON rating, but I'd have to drive a good bit for 1 octane and overpay to boot. I can get ethanol free, but again overpaying and most sell it midgrade instead of premium locally for some reason and I don't really see the major benefit aside from when the scooter sits. I use 93 E10, pumped into a 5 gallon jug... usually 3-5 gallons at a time... so there's less contamination of lower octane since most pumps are single hose for 3 grades and many discussions have been had about how much fuel you get is actually whatever was previously selected vs what you choose. Plus, the two people that I've rode with using the MVT and MHR ignitions, both curves I've used now, are using premium pump gas (91-93 AKI) with the same engine and had no significant trouble dialing in their 34mm PWKs with smaller, more common, jetting. The one thing that does bug me is that I expect EGT to change with timing anyway, because you're moving more or less of the combustion heat into the pipe depending on advance. CHT really doesn't seem to reflect changes there much with the LC setup, especially the more effective ones (modular heads). I got wider, more useful, swings with AC engines monitoring CHT. Fancy stuff that you're more likely to see in a research lab would tell a more detailed story, but I don't think I'll be getting a research grant anytime soon. I have a wideband, but I can see the thick smoke rings and the bowl not running low, so I'd rather not put a bung in the exhaust and foul out my sensor. As far as the actual cylinder cooling, I can pull in from a ride and put my hand on the outer head or cylinder so it's definitely not way hot. Coolant temp reading (from the outer head) shows 120-140F mostly right now. Might start rising a little with it now getting into real summer heat, but not a lot. If squish and chamber desing are good you dont have to worry about octane rating that much. My friend had a husq sm125 with 15:1 comp 1% squish smth like 0.7mm if im correct and VERY radical ignition and made over 32whp on a dyno where x-cw ktm 125 made 27whp and no detonation on pump eu 98e5 octane and a747 oil at 4.5% The fact that your cylinder is that cool after riding is strange my 94cc italkit am6 was like 80-90C (like what 160-170°f?) When sending hard and no detonation and it had a big radiator directly at airflow and it had a high flow wp (not sure about your pump flow and cooling capacity of your radiator setup ect) but your temps seem low for some reason, it would kinda mach with the scenario i explaines in dm=poor cylinder filling and lower power=weaker detonation so no immediate melting on first pull and no central detonation and plug melting the piston You are completely wrong in this octane rating is one the most important spec for the buil. This is how you destroy engines |
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tysta
Scoot Member
Posts: 79
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Post by tysta on Jun 17, 2024 10:49:02 GMT -5
I don't know that I can always hold the cylinder, but I can touch it and it's not burning me. Maybe not the smartest to go grabbing stuff, but real world I think a lot of us have touched enough coolant hose, heads, etc... to have some idea if it's way off. From what attention I do pay to CHT, it doesn't look way off either. The abnormal heat appears to be in the exhaust. The head is not modified from original. Squish is essentially to spec. Was 0.54mm last time with 0.55-0.6 as Malossi's spec, but with the gaskets 0.54 was the best I could do. It was either that or go more above 0.6 (forget the exact other option now), but I'd rather be 0.01 tighter. 0.54 is 1.23%, 0.55 would be 1.25% and I'd have to go to 0.44 to be at 1%. 0.01 should be insignificant and I've used 0.55 and larger with the same results on past assemblies. I'm curious what the advantage is of a carb sitting upright if the fuel level is known to work. John has suggested putting another pipe in the intake to level the carb, but I thought it was to be sure fuel supply was correct. I guess the difference in gravity could have some effect on how fuel is drawn up, but if anything wouldn't the angle actually make it easier for fuel to get up into the intake path vs having to go straight up? No one should manufacturer tilted bowl carbs if the tilted carb throws everything off. Thanks. I've said it before I think, but for anyone offering ideas or suggestions please don't take my comments as arguing. I'm thinking along and hoping that maybe for all of the expense and effort I will learn along the way. I'd rather question anyone than follow blindly with no understanding of why it's supposed to work. As happy as I'd be if this thing stopped trying to eat pistons, I'd be a bit sad if it quit and I didn't have a good idea of why. I have another person with an interesting theory about flow that makes sense, but they are PM-ing me so I want to make sure it's OK if I quote them here before I post their thoughts. Like you, here in the states (even in the same state as you), it's hard to get anything above 91/93 pump gas without spending an arm and a leg. I went through an issue with pinging/knock a while back with my bike when squish was set to .55mm. I tried using c12 and that cooled things down a bit and completely got rid of the detonation, but it didn't cool them down enough. I had to reset squish to be a little higher and set it to .68/.69mm and that helped even more but it still runs hot even with retarding the timing so I might increase it even more to .75/.8mm. When researching things, I came across a forum post on a two-stroke MX forum where they were talking about octane and residual fuel left in fuel lines from shared use of pumps for multiple octane fuels. When filling up small tanks of gas for 1-2 gallons for premix, be sure to throw a gallon or two of premium in your vehicle BEFORE filling your can. There is a small amount of fuel left in the pump line from the person that used it before you. And if they had used a lower octane fuel, then you are getting some of that too when you begin filling. I tested this when my motor was knocking - using this method and not, and I when I used it, it went away. I guess if you're filling a 20 gallon tank, the residual fuel is negligible, but when filling a gallon can, it can have an effect. It might be interesting to try race fuel too just to see if that cools things down for you. I know this might not have much of an effect on EGTs (probably would more with CHTs), and if you're anything like me don't want to be paying $20/gal for fuel, but it could provide you some more data to make your next move(s). Maybe there are some small airports out your way where you can get it cheaper than having to pay for a pail of VP c12 or something. I looked at what I could find of scoots in the Malossi racing series using RC1s at your suggestion long ago when I was having issues with the bowl draining in the VHST. My issue turned out to be fuel supply then, but it looked like they were just doing what I am and using whatever angle intake rubber rotation gave them. I think the one I use puts the carb at less angle than what the other RC1s I’ve been around use. From what I gather, and first-hand experience, the PWKs are more susceptible to odd behavior and issues as it pertains to their angle, at lower RPM, not high. On my MXS race scoot (mina vert - so the carb is facing left to right, not front to back), the idle can fluctuate and even stall the bike if I tip it to the left or right. It bugs me to not have a super crisp idle unless the bike is close to level, but apparently other guys have this issue too. Exactly Billy you went through a similar problem we watched that closely. I keep saying ignition/squish and will solve most problems |
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Post by xtremrox on Jun 17, 2024 11:33:45 GMT -5
If squish and chamber desing are good you dont have to worry about octane rating that much. My friend had a husq sm125 with 15:1 comp 1% squish smth like 0.7mm if im correct and VERY radical ignition and made over 32whp on a dyno where x-cw ktm 125 made 27whp and no detonation on pump eu 98e5 octane and a747 oil at 4.5% The fact that your cylinder is that cool after riding is strange my 94cc italkit am6 was like 80-90C (like what 160-170°f?) When sending hard and no detonation and it had a big radiator directly at airflow and it had a high flow wp (not sure about your pump flow and cooling capacity of your radiator setup ect) but your temps seem low for some reason, it would kinda mach with the scenario i explaines in dm=poor cylinder filling and lower power=weaker detonation so no immediate melting on first pull and no central detonation and plug melting the piston You are completely wrong in this octane rating is one the most important spec for the buil. This is how you destroy engines I meant that pump gas will do after that no race gas 100 octane needed |
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Post by xtremrox on Jun 17, 2024 11:36:55 GMT -5
Like you, here in the states (even in the same state as you), it's hard to get anything above 91/93 pump gas without spending an arm and a leg. I went through an issue with pinging/knock a while back with my bike when squish was set to .55mm. I tried using c12 and that cooled things down a bit and completely got rid of the detonation, but it didn't cool them down enough. I had to reset squish to be a little higher and set it to .68/.69mm and that helped even more but it still runs hot even with retarding the timing so I might increase it even more to .75/.8mm. When researching things, I came across a forum post on a two-stroke MX forum where they were talking about octane and residual fuel left in fuel lines from shared use of pumps for multiple octane fuels. When filling up small tanks of gas for 1-2 gallons for premix, be sure to throw a gallon or two of premium in your vehicle BEFORE filling your can. There is a small amount of fuel left in the pump line from the person that used it before you. And if they had used a lower octane fuel, then you are getting some of that too when you begin filling. I tested this when my motor was knocking - using this method and not, and I when I used it, it went away. I guess if you're filling a 20 gallon tank, the residual fuel is negligible, but when filling a gallon can, it can have an effect. It might be interesting to try race fuel too just to see if that cools things down for you. I know this might not have much of an effect on EGTs (probably would more with CHTs), and if you're anything like me don't want to be paying $20/gal for fuel, but it could provide you some more data to make your next move(s). Maybe there are some small airports out your way where you can get it cheaper than having to pay for a pail of VP c12 or something. From what I gather, and first-hand experience, the PWKs are more susceptible to odd behavior and issues as it pertains to their angle, at lower RPM, not high. On my MXS race scoot (mina vert - so the carb is facing left to right, not front to back), the idle can fluctuate and even stall the bike if I tip it to the left or right. It bugs me to not have a super crisp idle unless the bike is close to level, but apparently other guys have this issue too. Exactly Billy you went through a similar problem we watched that closely. I keep saying ignition/squish and will solve most problems But i dont understand how larger squish helps anything it makes detonation just more likely. 15:1 and 14:1 has been run on 2 strokes with 98 many many many times And as far as i know pump 93 there is bit better than our 98e5 |
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tysta
Scoot Member
Posts: 79
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Post by tysta on Jun 17, 2024 13:14:33 GMT -5
Exactly Billy you went through a similar problem we watched that closely. I keep saying ignition/squish and will solve most problems But i dont understand how larger squish helps anything it makes detonation just more likely. 15:1 and 14:1 has been run on 2 strokes with 98 many many many times And as far as i know pump 93 there is bit better than our 98e5 Define larger?!!! Squish band should be at least 50% of the bore diameter The Squish value is something else. And yes tighter Squish help with knocking. |
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Post by 90GTVert on Jun 17, 2024 13:31:59 GMT -5
xtremrox is the person I referred to with other ideas from private messages, and he said it's fine to post it so here is that conversation. (I'm not using quotes so it doesn't make it as cluttered.)
xtremroxHey im jimi from finland i have EXTENSIVE knowledge of 2 strokes i have built few of the fastest 125cc street bikes in finland and ported tens of these 50-125 bikes and help tune hundreds. So i have noticed few problems on your build that restrit power and performance a lot i think 1.Your engine seems and acts "under tuned" or restricted by f/a mixture in cylinder, your driving rpm range seems rigth and no slippage is detected, The first pwk tuning video made me realize it, your engine is wasting f/a mixture my 94cc ported custom head insert and a voca bb exhaust on am6 engine (crankcase volume ect close to stock minarelli) used 140? Main jet and went close to 100mph caculated power being close to 25hp. So somehow your mixture is being wasted and you need huge jets to rich it out and put egts low. I analyzed the build and realized the case matching you did on the cylinder side caused a change in the important B transfer duct flow area and i think its causing mixture flow problems and lot of it is going to the exhaust and causing the high egt and fake leaning. 2.your carb/intake matching i know certainly that the pwk engine side wall is very thick and it has a edge inside the intake (looking from engine side of intake the carb engine side "wall is visible) that causes huge turbulance [/quote]
90GTVertMine uses 140-150 MJ with the 28mm, but 34mm it’s been 200-220. If port matching does it, it doesn’t do it with the 28mm. What’s weird if it’s low on power is that I’m 300 pounds and tall and can’t tuck down and still have done 85MPH and I don’t even tune for speed. I’m 0.6 seconds slower in the 1/8 mile than a friend’s RC1 that he could launch wide open while I’m rolling in because it will wheelie and his is low to the ground while mine’s tall and I’m at least 150 pounds heavier than him and his scooter. I rode with a guy not half my size on another RC1 with a 34mm PWK and he couldn’t keep up. If mine is out of tune and malfunctioning, some must be way out. I did notice a trail of carbon behind the bridge in the exhaust port, but I’ve also been putting a ton of fuel to it lately with the PWK. Thank you for the info/suggestions. I do agree that it seems like it’s wasting fuel now. It’s weird to go higher and higher and watch EGT not drop even with fuel showing on the plug.
xtremroxIf the carbon has deposited in a symmetrical manner after the bridge and starts from a defined point its a sing of failing transfer collum. The collum should form towards the rear of the cyl and cause 3 vortexes 1 that rotates clockwise towards the exhaust viewed from the side, and 2 smaller ones that rotate towards each side starting from about rear wall of tranfer b viewed from the top and switch more towards the exhaust as the piston rises. These vortesies help keep the mixture in the cylinder while the low pressure wave caused by the exhaust diffuser cone sucks the mixture from the transfers and a bit from the case transfer area. A bit of mixture goes to the exhaust with the negative pressure wave, but the piston also causes mixture from deeper in the cases to enter the cylinder and at transfer closing the cylinder fill is very close to 100%. Then a positive pressure return wave,caused by the exhaust of the previous stroke and the bit of fresh mix that previusly went to the exhaust hitting the baffle cone pushes the extra mix back to the cylinder at the last moment before piston closes the exhaust. Therefore the cylinder fill is over 100%( i know you bropably know all of this but its easier to explain my theory this way) So what i think is happening, the volume change in transfer b caused the flow resistance and speed to change (larger bottom part of transfer duct so when that larger volume has to go through the smaller cross area of the upper Part and the port itself it causes pressure increase and flow speed reduction) So the vortexes wont form properly and the fuel of transfer b arrives bit later just for the negative pulse and a LOT of fuel goes to the exhaust, so cylinder fill is very low exspecisly at the "pipe range" and the return pulse cant fix that enough so final cylinder fill is still below 100% and a lot of fuel gets left behind in the cylinder exhaust duct. This causes 3 things 1.The vortesies are a must for smooth fast burn and good cylinder pressure curve, so without them the burn is slow and torque is much lower than expected 2.The now underfilled (lean also will explain this in a moment)not properly mixed compustion is slow but has lot of hotspots and cold spots so the burn can result in strange phenoman i call exhaust stroke ignition. Now in the cylinder you have areas of left over fuel and left over oxygen seperated by exhaust gasses.remember the negative pressure wave? Now that sucks all the gasses out and also fresh mix after it so it ignites in the proximity of the exhaust bridge and shortly after that, usually after the bridge where the 2 sides collide it is so hot it causes carbon deposition and mega high egt that seems to impossible to tame and tuning becomes impossible also(you need huge jet to tame the egt but no big change in power as the cylinder fill never reaches anything good) 3.So i talked about lean burn, yes remember when i said the collum has collapsed? So that causes a empty spot in the cylinder that has to be filled that is then filled by the very lean mix that comes in last through the reeds when air velocity no more draws fuel sufficently, now you have fresh air bubble in the cylinder usually in the rear upper area (where your piston failed) So this all causes high tempatures in the exhaust port area and the rear of the cylinder(where your piston seems to be most melted and damaged) Also the carbon deposit pattern on your piston tells it all the scavening and burn are all over the place and no transfer pattern is observable The 34mm carb makes this so much worse becouse slower flow speed that makes the scavenging problems even more dangerous Also this scenario explains why you need much more advance than is safe to be able to use normal jet sizes as that increases pcp exponentialy and gives the badly mixed fuel more time to burn BUT leads to detonation and in your case the previus problems hide detonation sings and you dont expect it at all becouse of the normal egt and not peak performance. In my experience all high end 90~+cc engines can reach figures of 6s or lower 0-60mph. For example my minarelli stock case 88cc airsal went 5.8s and i weigth 88kg and the scooter was a big aerox with super heavy subframe and brakes. My friends ported 86tpr went 5.5 and bidalot flat 5.0. The 94 testarossa should be more powerful than any off these in my opinion as it has VERY good transfer desing and good timing/areas/blowdown. Here a stock case version 94cc went 5.x sec also with 28pwk and most exhaust(i suggest you try most 90/100cc exhaust it is a very good desing) one thing that i think many pepole get bamboozled by is 2 stroke exhaust, the cc ratings are not that accurate for example here the most powerful 70cc engine run 80/90 pipes and 50cc run 70/80 pies ect. In a very grude explanstion, better transfer geometry allows steeper diffuser and baffle angles and cylinder fill. The volume of the pipe effects rpm range and peak power and is the Part most effect by cc=small engines with high peak power rpm and small power range can use very very big volume pipes=lower hp/l engines with more displacement can use same exhaust so the cc rating is not so accurate i would say that if you want really good power opt for the most radically shaped exhaust (big belly and steep end cones) but to solve your problems i suggest a 28mm or maxium 30mm pwk carb and fixing the transfer duct with epoxy or porting the rest of it
90GTVertI can't believe I don't seem to have a pic or video of the port before I cleaned it, but somehow I didn't get one. It's very simply a trail behind the divider. Very thin. Widest just after the divider, tapering off as it goes toward the exit. When I first saw it, I figured this was just a sign that the divider probably needs some sort of reshaping so flow is not dead back there. I could be mistaken and it's been there in the past too. This makes some sense to me. The only thing that throws a bit of a wrench in the idea is that I replaced the cylinder kit recently (due to damage from all of the issues combined with thousands of miles) and I was quick with the matching of the cylinder and don't think it's done quite like the previous one, but the issue hasn't subsided. I will have to look it all over better. With my memory and the amount of times I've taken it apart lately paired with the rest of life in general, it's hard to remember it all with great certainty.
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Post by xtremrox on Jun 17, 2024 15:09:46 GMT -5
But i dont understand how larger squish helps anything it makes detonation just more likely. 15:1 and 14:1 has been run on 2 strokes with 98 many many many times And as far as i know pump 93 there is bit better than our 98e5 Define larger?!!! Squish band should be at least 50% of the bore diameter The Squish value is something else. And yes tighter Squish help with knocking. Yes i meant how larger squish gap helps the knock problem or maybe i understood something wrong in what he ment by "going up in squish more like to 0.7~ would maybe help" |
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Post by billwill on Jun 17, 2024 15:47:58 GMT -5
This is getting to be quite interesting and the dialogue and back and forth is what keeps bringing me back here.
I'll say it again, I think you should at least TRY running fuel with a higher octane rating and/or adjusting squish to be something higher around .7mm or more. I know for you with a water-cooled kit, adjusting squish is probably the last thing you want to do but I think you may see an improvement.
For what it's worth, when I went from .49mm or so to .69mm, I didn't feel any noticeable loss of power. Heck, next thing I want to do to my scoot to make it more ridable is up the squish to .8mm with hopes of cooling it down a bit.
Another thing I'm thinking of was the fact that I broke two exhaust pipes recently right at the first bend of the pipe. A lot of people were saying how it was mounted poorly or with stress on the pipe, which could be true, but since I've retarded my timing and adjusted squish, it hasn't happened since. I wonder if my EGTs were way high, I just have no way of knowing for sure since I don't run a gauge.
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Post by xtremrox on Jun 17, 2024 16:45:18 GMT -5
This is getting to be quite interesting and the dialogue and back and forth is what keeps bringing me back here. I'll say it again, I think you should at least TRY running fuel with a higher octane rating and/or adjusting squish to be something higher around .7mm or more. I know for you with a water-cooled kit, adjusting squish is probably the last thing you want to do but I think you may see an improvement. For what it's worth, when I went from .49mm or so to .69mm, I didn't feel any noticeable loss of power. Heck, next thing I want to do to my scoot to make it more ridable is up the squish to .8mm with hopes of cooling it down a bit. Another thing I'm thinking of was the fact that I broke two exhaust pipes recently right at the first bend of the pipe. A lot of people were saying how it was mounted poorly or with stress on the pipe, which could be true, but since I've retarded my timing and adjusted squish, it hasn't happened since. I wonder if my EGTs were way high, I just have no way of knowing for sure since I don't run a gauge. Just why would he make squish gap larger in a well desinged setup like this. It only has drawbacks (more likely to detonate if tuning for power slower combustion and worse thermal effinency😢 |
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tysta
Scoot Member
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Post by tysta on Jun 17, 2024 17:40:30 GMT -5
xtremrox is the person I referred to with other ideas from private messages, and he said it's fine to post it so here is that conversation. (I'm not using quotes so it doesn't make it as cluttered.)
xtremroxHey im jimi from finland i have EXTENSIVE knowledge of 2 strokes i have built few of the fastest 125cc street bikes in finland and ported tens of these 50-125 bikes and help tune hundreds. So i have noticed few problems on your build that restrit power and performance a lot i think 1.Your engine seems and acts "under tuned" or restricted by f/a mixture in cylinder, your driving rpm range seems rigth and no slippage is detected, The first pwk tuning video made me realize it, your engine is wasting f/a mixture my 94cc ported custom head insert and a voca bb exhaust on am6 engine (crankcase volume ect close to stock minarelli) used 140? Main jet and went close to 100mph caculated power being close to 25hp. So somehow your mixture is being wasted and you need huge jets to rich it out and put egts low. I analyzed the build and realized the case matching you did on the cylinder side caused a change in the important B transfer duct flow area and i think its causing mixture flow problems and lot of it is going to the exhaust and causing the high egt and fake leaning. 2.your carb/intake matching i know certainly that the pwk engine side wall is very thick and it has a edge inside the intake (looking from engine side of intake the carb engine side "wall is visible) that causes huge turbulance
90GTVertMine uses 140-150 MJ with the 28mm, but 34mm it’s been 200-220. If port matching does it, it doesn’t do it with the 28mm. What’s weird if it’s low on power is that I’m 300 pounds and tall and can’t tuck down and still have done 85MPH and I don’t even tune for speed. I’m 0.6 seconds slower in the 1/8 mile than a friend’s RC1 that he could launch wide open while I’m rolling in because it will wheelie and his is low to the ground while mine’s tall and I’m at least 150 pounds heavier than him and his scooter. I rode with a guy not half my size on another RC1 with a 34mm PWK and he couldn’t keep up. If mine is out of tune and malfunctioning, some must be way out. I did notice a trail of carbon behind the bridge in the exhaust port, but I’ve also been putting a ton of fuel to it lately with the PWK. Thank you for the info/suggestions. I do agree that it seems like it’s wasting fuel now. It’s weird to go higher and higher and watch EGT not drop even with fuel showing on the plug.
xtremroxIf the carbon has deposited in a symmetrical manner after the bridge and starts from a defined point its a sing of failing transfer collum. The collum should form towards the rear of the cyl and cause 3 vortexes 1 that rotates clockwise towards the exhaust viewed from the side, and 2 smaller ones that rotate towards each side starting from about rear wall of tranfer b viewed from the top and switch more towards the exhaust as the piston rises. These vortesies help keep the mixture in the cylinder while the low pressure wave caused by the exhaust diffuser cone sucks the mixture from the transfers and a bit from the case transfer area. A bit of mixture goes to the exhaust with the negative pressure wave, but the piston also causes mixture from deeper in the cases to enter the cylinder and at transfer closing the cylinder fill is very close to 100%. Then a positive pressure return wave,caused by the exhaust of the previous stroke and the bit of fresh mix that previusly went to the exhaust hitting the baffle cone pushes the extra mix back to the cylinder at the last moment before piston closes the exhaust. Therefore the cylinder fill is over 100%( i know you bropably know all of this but its easier to explain my theory this way) So what i think is happening, the volume change in transfer b caused the flow resistance and speed to change (larger bottom part of transfer duct so when that larger volume has to go through the smaller cross area of the upper Part and the port itself it causes pressure increase and flow speed reduction) So the vortexes wont form properly and the fuel of transfer b arrives bit later just for the negative pulse and a LOT of fuel goes to the exhaust, so cylinder fill is very low exspecisly at the "pipe range" and the return pulse cant fix that enough so final cylinder fill is still below 100% and a lot of fuel gets left behind in the cylinder exhaust duct. This causes 3 things 1.The vortesies are a must for smooth fast burn and good cylinder pressure curve, so without them the burn is slow and torque is much lower than expected 2.The now underfilled (lean also will explain this in a moment)not properly mixed compustion is slow but has lot of hotspots and cold spots so the burn can result in strange phenoman i call exhaust stroke ignition. Now in the cylinder you have areas of left over fuel and left over oxygen seperated by exhaust gasses.remember the negative pressure wave? Now that sucks all the gasses out and also fresh mix after it so it ignites in the proximity of the exhaust bridge and shortly after that, usually after the bridge where the 2 sides collide it is so hot it causes carbon deposition and mega high egt that seems to impossible to tame and tuning becomes impossible also(you need huge jet to tame the egt but no big change in power as the cylinder fill never reaches anything good) 3.So i talked about lean burn, yes remember when i said the collum has collapsed? So that causes a empty spot in the cylinder that has to be filled that is then filled by the very lean mix that comes in last through the reeds when air velocity no more draws fuel sufficently, now you have fresh air bubble in the cylinder usually in the rear upper area (where your piston failed) So this all causes high tempatures in the exhaust port area and the rear of the cylinder(where your piston seems to be most melted and damaged) Also the carbon deposit pattern on your piston tells it all the scavening and burn are all over the place and no transfer pattern is observable The 34mm carb makes this so much worse becouse slower flow speed that makes the scavenging problems even more dangerous Also this scenario explains why you need much more advance than is safe to be able to use normal jet sizes as that increases pcp exponentialy and gives the badly mixed fuel more time to burn BUT leads to detonation and in your case the previus problems hide detonation sings and you dont expect it at all becouse of the normal egt and not peak performance. In my experience all high end 90~+cc engines can reach figures of 6s or lower 0-60mph. For example my minarelli stock case 88cc airsal went 5.8s and i weigth 88kg and the scooter was a big aerox with super heavy subframe and brakes. My friends ported 86tpr went 5.5 and bidalot flat 5.0. The 94 testarossa should be more powerful than any off these in my opinion as it has VERY good transfer desing and good timing/areas/blowdown. Here a stock case version 94cc went 5.x sec also with 28pwk and most exhaust(i suggest you try most 90/100cc exhaust it is a very good desing) one thing that i think many pepole get bamboozled by is 2 stroke exhaust, the cc ratings are not that accurate for example here the most powerful 70cc engine run 80/90 pipes and 50cc run 70/80 pies ect. In a very grude explanstion, better transfer geometry allows steeper diffuser and baffle angles and cylinder fill. The volume of the pipe effects rpm range and peak power and is the Part most effect by cc=small engines with high peak power rpm and small power range can use very very big volume pipes=lower hp/l engines with more displacement can use same exhaust so the cc rating is not so accurate i would say that if you want really good power opt for the most radically shaped exhaust (big belly and steep end cones) but to solve your problems i suggest a 28mm or maxium 30mm pwk carb and fixing the transfer duct with epoxy or porting the rest of it
90GTVertI can't believe I don't seem to have a pic or video of the port before I cleaned it, but somehow I didn't get one. It's very simply a trail behind the divider. Very thin. Widest just after the divider, tapering off as it goes toward the exit. When I first saw it, I figured this was just a sign that the divider probably needs some sort of reshaping so flow is not dead back there. I could be mistaken and it's been there in the past too. This makes some sense to me. The only thing that throws a bit of a wrench in the idea is that I replaced the cylinder kit recently (due to damage from all of the issues combined with thousands of miles) and I was quick with the matching of the cylinder and don't think it's done quite like the previous one, but the issue hasn't subsided. I will have to look it all over better. With my memory and the amount of times I've taken it apart lately paired with the rest of life in general, it's hard to remember it all with great certainty.
[/quote] So if you go back on my comments you will see I refer to engine setup also intake speed. I did watch those steps were apparently you touched the cylinder/cases I Don't know but I kinda suspected something was wrong here He is right on what he says. Very low intake speed and not enough (turbulence) let's say to make it easier to understand. ! |
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