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Post by 90GTVert on Nov 19, 2023 7:26:06 GMT -5
I forgot to mention this, but on a lighter note...
When I did a test ride yesterday, I passed a house with a few young kids in a front yard holding onto a standard size American flag blowing straight out in the strong wind. They saw me coming an waved so I blipped the throttle a few times and went WOT. They were jumping around waving and fist pumping. I couldn't resist doing it again for a similar reaction on my way back. It's just not every day that you see people showing the proper amount of enthusiasm when a two-stroke passes. Meanwhile their parents were prob inside wondering what that god-awful noise was. 🤣
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Post by 190mech on Nov 19, 2023 17:03:46 GMT -5
Thin the needle tip area .002" with cordless drill and sandpaper and see how it acts, Ive done that a few times back in the day..
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Post by 90GTVert on Nov 20, 2023 9:33:08 GMT -5
I was thinking about what could be happening in the engine. My first thought was, perhaps the larger carburetor has increased the cylinder filling or load. If the big carb is doing it's job, and it looks like it is based on seeing some performance gains, then it should allow for better cylinder filling. If it's allowing more air and fuel into the cylinder, then the mixture should be more dense. Greater mixture density and better mixture quality, from something like a change in fuel droplet size for example, may require less ignition advance. I'm not convinced that this is what's happening, but it's an idea. Then I started thinking about Ryan's engine vs mine. We have the same EGT setup with similar placement. Mine's 1400+ with what we'd expect to be reasonable jetting sizes and his is "normal"... say 1200-1350. He has the same cylinder and neither of ours are ported. Same combustion chamber size. Similar squish. Same crankcases, though I believe mine are just slightly more ported or smoothed really. Same reeds. Different intakes and different pipes... but he did use the same exhaust that I use for a long time. I've tried his carb and filter so I know it's not just my carb/filter. That leaves ignition. I have an MVT and he has the Selettra that comes with the RC-1. If setup and matching Malossi's specs, he should have something like 2-5 degrees more ignition advance at peak power RPM than I have. I have a lot more advance at lower RPM. This is a graph that I made awhile back when I was considering advancing my timing to match the MHR more closely in peak power range. This confuses the thought. Too much ignition advance if working with a mixture that can support greater flame speed could increase EGT. On the other hand, not enough advance could have more of the combustion event traveling downstream toward the EGT sensor and increasing readings. Typically my sign to back off ignition advance is hearing spark knock or seeing signs of detonation or if I try other settings and it accelerates more quickly with different timing. I have not noticed signs of detonation. Combining that with assuming that Ryan has Malossi's specified timing that has more advance at high revs makes me think that I'd be more likely to need to bump up my timing a little... if timing indeed has anything to do with it. I did test 3 degrees of advance and retard with an MVT DD on my TPR 86cc that had the same base timing setting as I do now. In that case I found that I picked up a couple of tenths in acceleration by advancing the timing 3 degrees. I was also thinking that not enough advance could explain high readings that should be trying to melt a piston but generally don't seem to be. If the heat is traveling into the exhaust more instead of hanging around the piston longer, then that could do it. I did have the soft-seize situation with a max of 1303 EGT, but that was 1/2 throttle and could very well be from lean settings there. 100 degrees hotter WOT has not caused it to die... yet... OK now everyone cross their fingers and toes that I didn't just jinx myself. ...And then there's the thought that it probably hasn't changed so much from the larger carb that this is the case. 100-150 degree change may not happen with just a few degrees of timing. Never tried it before with an EGT. It may be more likely that it's just a carb tuning issue like the needle or needle jet. What makes me veer away from that to some degree is that it did run pretty strong around a 215 main jet. It felt and sounded a bit rich as I went larger or took the main jet out to make EGT decrease... though from 215 to 250 it only changed ~0.2 in the 1/8 mile.
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tysta
Scoot Member
Posts: 74
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Post by tysta on Nov 21, 2023 13:39:55 GMT -5
I was thinking about what could be happening in the engine. My first thought was, perhaps the larger carburetor has increased the cylinder filling or load. If the big carb is doing it's job, and it looks like it is based on seeing some performance gains, then it should allow for better cylinder filling. If it's allowing more air and fuel into the cylinder, then the mixture should be more dense. Greater mixture density and better mixture quality, from something like a change in fuel droplet size for example, may require less ignition advance. I'm not convinced that this is what's happening, but it's an idea. Then I started thinking about Ryan's engine vs mine. We have the same EGT setup with similar placement. Mine's 1400+ with what we'd expect to be reasonable jetting sizes and his is "normal"... say 1200-1350. He has the same cylinder and neither of ours are ported. Same combustion chamber size. Similar squish. Same crankcases, though I believe mine are just slightly more ported or smoothed really. Same reeds. Different intakes and different pipes... but he did use the same exhaust that I use for a long time. I've tried his carb and filter so I know it's not just my carb/filter. That leaves ignition. I have an MVT and he has the Selettra that comes with the RC-1. If setup and matching Malossi's specs, he should have something like 2-5 degrees more ignition advance at peak power RPM than I have. I have a lot more advance at lower RPM. This is a graph that I made awhile back when I was considering advancing my timing to match the MHR more closely in peak power range. This confuses the thought. Too much ignition advance if working with a mixture that can support greater flame speed could increase EGT. On the other hand, not enough advance could have more of the combustion event traveling downstream toward the EGT sensor and increasing readings. Typically my sign to back off ignition advance is hearing spark knock or seeing signs of detonation or if I try other settings and it accelerates more quickly with different timing. I have not noticed signs of detonation. Combining that with assuming that Ryan has Malossi's specified timing that has more advance at high revs makes me think that I'd be more likely to need to bump up my timing a little... if timing indeed has anything to do with it. I did test 3 degrees of advance and retard with an MVT DD on my TPR 86cc that had the same base timing setting as I do now. In that case I found that I picked up a couple of tenths in acceleration by advancing the timing 3 degrees. I was also thinking that not enough advance could explain high readings that should be trying to melt a piston but generally don't seem to be. If the heat is traveling into the exhaust more instead of hanging around the piston longer, then that could do it. I did have the soft-seize situation with a max of 1303 EGT, but that was 1/2 throttle and could very well be from lean settings there. 100 degrees hotter WOT has not caused it to die... yet... OK now everyone cross their fingers and toes that I didn't just jinx myself. ...And then there's the thought that it probably hasn't changed so much from the larger carb that this is the case. 100-150 degree change may not happen with just a few degrees of timing. Never tried it before with an EGT. It may be more likely that it's just a carb tuning issue like the needle or needle jet. What makes me veer away from that to some degree is that it did run pretty strong around a 215 main jet. It felt and sounded a bit rich as I went larger or took the main jet out to make EGT decrease... though from 215 to 250 it only changed ~0.2 in the 1/8 mile. Like i mentioned before the mvt isn't the right setup. Understand also the mvt have that stupid dual spark Every single engine I used the mvt always requires a gigantic jet. Last ar cooled 70cc3 I build set to rev 12000 with a 28mm pwk carb was using a 190 jet...
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Post by 90GTVert on Nov 21, 2023 17:11:03 GMT -5
Like i mentioned before the mvt isn't the right setup. Understand also the mvt have that stupid dual spark Every single engine I used the mvt always requires a gigantic jet. Last ar cooled 70cc3 I build set to rev 12000 with a 28mm pwk carb was using a 190 jet... Here's the part that I don't get if questioning the MVT... Why does it work with everything except the PWK? I have the 150MJ that comes in the VHST for the RC-1 in there (I have tried other jets). I didn't have any wild jet in the PHBL on the TPR with MVT DD. The PWK runs 1400 or near enough without huge jets. I put the VHST back on and everything is fine again.
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Post by Lucass2T on Nov 22, 2023 3:05:03 GMT -5
Throw the pwk in the ultrasonic cleaner. Maybe some debris or dust or whatever got inside.
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Post by 90GTVert on Nov 22, 2023 7:31:41 GMT -5
Throw the pwk in the ultrasonic cleaner. Maybe some debris or dust or whatever got inside. It's been cleaned before I ever used it and again, but it also works the same as Ryan's.
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Post by 90GTVert on Nov 23, 2023 0:00:20 GMT -5
I put the PWK back on today. I did a set of runs with a 215 main jet and standard timing (0.35mm BTDC).
Avg 1/8 mile : 9.93 @ 65.81 Avg EGT @ 60MPH during acceleration : 1321
I then changed timing so that the marks on the ignition align at 0.62mm BTDC. 3° more ignition advance.
Avg 1/8 mile : 11.59 @ 55.95 Avg EGT @ 60MPH during acceleration : 1150
EGT was way down, but so was performance. When I first started the scoot, idle was off. It seemed like the mix was wrong. I'd guess lean, but didn't adjust. It felt OK once warm and ran well, till I tried to go WOT. WOT was clearly wrong. I would think lean, but may have been rich. Numbers look more like rich. I decided to give it another try before coming home and did another set of runs where WOT felt better for some reason (though still not right).
Avg 1/8 mile : 10.44 @ 61.83 Avg EGT @ 60MPH during acceleration : 1201
I may or may not have made progress here. It certainly seems like the jetting requirement has changed. It could go back to 1400 EGT by the time it feels right though. Didn't get that far. With the VHST and standard timing, I was typically very high 1100s to mid 1200s @ 60 so it's close there even though WOT is not good. Kinda wild to see the performance swing. I could go through a pile of jets before without seeing that much difference. From about 190 to no main jet at all had roughly an 0.5 second difference in the 1/8 in past tests.
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Post by 90GTVert on Nov 23, 2023 21:44:55 GMT -5
I wanted to try out some main jets today to see if I really did get somewhere with the ignition advance. I switched from the 215 to a 200 and fired up the scoot, only to hear a metallic sort of jingle sound. Seemed like it was coming from the CVT so I pulled the cover and found the front pulley loose… again. I wound up replacing the starter pawl because it and the crank had some mild damage to the splines. I’m really not sure why it wants to come loose lately, but I used thread locker more liberally and torqued to 32.5 instead of 32 ft-lb (the high side of the torque spec that I always use). Then I decided to make use of the holiday. Instead of going back and forth to my test run spots which are 2-7 miles away for every jet change (not really places where I should hang out all day), I went to an industrial park. I carried a jet kit and the tools to do swaps along. I figured not many people would be around on Thanksgiving and the road turned out to be just long enough to do 1/8 mile runs and get stopped from 65-70MPH. That worked out well. Pretty nice to do runs, stop right there and change jets, do more runs and so on… I tested 180, 185, 190, 195, 200 and 205. I haven’t had time to go over data because I came back for dinner and then we discovered that the freezer stopped working so I wound up bagging our stuff up and taking it to my uncle’s where he had free space in a big upright. Anyway, it got too hot on the small end of jetting and cool and felt rich on the big end of jets. I’m guessing 190-195 will be about right. Mainly it was nice to see it act much more like I expected it to from day 1 so I think the timing change was a success. Idle still seems off and it gets a little boggy sometimes so it may need a bigger pilot now. Didn’t mess with any higher part throttle settings on the trip there and back, but it did fine cruising around at low 1/8 to 1/4 throttle positions. The industrial park spoiled me and now I wish I had a spot like that on non-holidays. Tuning is so much better right back to back without rides to and from. I think if I sat beside the road and did this in my usual spots I’d wind up getting to meet the Sheriff sooner or later.
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Post by oldgeek on Nov 23, 2023 22:53:56 GMT -5
Excellent work finding out the real problem. That one sure was a head scratcher for a while. But now you can finally move on to getting that carb dialed in and see your true gains from using it.
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Post by 90GTVert on Nov 24, 2023 14:02:50 GMT -5
I put a 192 main jet in. Looks like best performance is 185-190. 190 is fine for EGT for 1/8 mile, but I think it’s gonna be hot beyond that. 192 prob won’t be much different, but maybe some slight safety margin.
Haven’t tested it yet. The guys I rode with in OC at the last car show just invited me to a meet about 25 miles away tonight. I’m saving my cold weather tolerance for that, cause it’ll be 30s and 40s. Kinda wanna take T2 but I’ll prob just take the TMAX over since I’ll be riding through the countryside at night both ways. Not terrifying at all in peak deer season.
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Post by 90GTVert on Dec 2, 2023 12:03:19 GMT -5
The scoot was slow when I tested with the 192 main a few days ago. Hmmm. Looked like it should be on the safer side, but OK. I tried a couple of needle changes as well that day. I tried moving the clip down 1 from center on the HLJ to richen part throttle a little and also tried an HKJ needle with the clip in the center. The richer setting on the HLJ seemed to help a little with part throttle temps (not much) and still ran OK so I went with that.
It was very windy for the last tests, but decent weather 50F and above without rain/wind/fog... is tough to get right now. I thought maybe the fairly harsh winds threw times off so I wanted to retest. Still slow.
I put a 190 main in, thinking I know that worked when last tested. Still slow. 8-9 sec 0-60s and 10.30-50 1/8 mile. It felt wrong on takeoff. Probably slip. I looked at the dragy and it was slow. My hands and wrists have been hurting and numb (sounds odd but they can be both at the same time) and I thought maybe that had something to do with throttle control because it isn't a high revving very obvious slip. I stopped and did 2 quick launches just to see 60fts and made sure I used enough throttle. 2.55 seconds average. I should be able to do 2.3X anytime and really good runs for me are 2.2X or occasionally a 2.1X.
Definitely a CVT issue. I've probably once again worn the belt enough to make it slip a little more.
I took the CVT apart last night. I intended to swap the seal in the Polini Hi-Speed vari and go back to using that since it did make me slightly quicker in past tests. Made a 4mm spacer to go behind the vari this morning. Went to put the seal in and it won't fit. Turns out what looked like 29 on the seal was 28... so I got one that's too large. I wound up just putting some sealant around the outside of the old seal and putting it back in. 5.25g weights and 0.75mm of shims that hopefully work with the now ~ 18.9mm belt with 1,534 miles on it.
I got invited to another meet today near Dover, DE with bikes and cars. I hustled to get the spacer made and swap done, hoping to take T2 there. I'd have to leave soon to make it and it's still dense fog and wet roads. I'm not driving 1.5 hours each way to hang out and ride in that with no test runs and suspect not many others show up.
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Post by 90GTVert on Dec 4, 2023 19:59:04 GMT -5
Finally got some dry weather to do test passes. Didn't go great.
It's still slow. Felt like slip at first with 0.75mm shims. Avg 10.49 @ 65.55 with terrible 2.62 60ft and 3.11 0-30.
I swapped to an 0.5mm shim. Found some wear on the fixed half and shim so I put the fixed half in the lathe and cut the center a little flatter and resurfaced it with sandpaper to help it slip less. Fouled a plug or maybe bad contact from a worn tip on the first try. Came back and switched the plug out. The old plug had black threads, dark base with wetting, and light cardboard porcelain. The light porcelain concerned me a little since it wasn't looking washed like I see if it's real rich so I cut the plug apart. Mix ring looks good. So the plug seems to tell me that it's rich at low throttle, on the lean side mid throttle and then fine WOT... which is exactly what I would have guessed from all other indications. Still slow, but improved to 10.11 @ 65.29 with still not quite right 2.44 60ft and 2.65 0-30.
Then I took all shims out, but the belt couldn't make it to the outside of the rear pulley. Wound up at 0.3mm shims for the last test of the day. I thought it could still use a little more shimming, but I wanted to see what it did and it was at least close to letting the belt reach all the way out. 10.07 @ 65.39, 2.46 60ft, 2.67 0-30.
I'm looking for mid-high 9 averages. It's still wrong though. I noticed that with less shimming it felt like the jet was wrong up top. It didn't pull well and started feeling rich at the end of the run. Looked at the data just now and it's because RPM is dropping at speed.
With 0.75mm shimming RPM goes from 13,730 @ 30MPH to 13,905 @ 60MPH. With 0.5mm shimming RPM goes from 13,505 @ 30MPH to 13,015 @ 60MPH. With 0.3mm shimming RPM goes from 13,545 @ 30MPH to 12,755 @ 60MPH.
So it looks like there is an ideal shimming point to get RPM to stay steady... probably 0.6-0.7mm based on those results. It felt like it still slipped some at takeoff though. I wish the fixed half was like new, and I did order another from ScooterPartsCo, but I don't really think it's a problem. I'm wondering if I'm at the end of the high performance life of the belt with this setup. I hope not. It's around 18.9mm with a 19.5mm spec... but some that I have came new at around 19.2mm and others have been about 19.5mm. The 19.2mm belts wouldn't have a long life at that rate. Still a far cry from past setups blowing belts at 200 miles, but having 1 belt for 1,500+ miles has been nice and the belt really should go to 18.5 or so before it would be service limit range. I dunno what the spec is, but generally at least 1mm of wear is allowed in stock stuff.
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Post by 90GTVert on Dec 5, 2023 23:15:02 GMT -5
I put in an 0.6mm shim and did some test runs today. That definitely worked to keep RPM tighter for acceleration runs, with averages staying with ~100RPM from 30-60MPH. It's also closer to it's typical best RPM range, though not quite there. I organized my shims so I don't have to measure every one every time while I was at it. It started breaking up again on the first set of runs and I decided to change the spark plug cap, which I didn't replace with the plug. I had to use a pry bar to pop the cap off because it was so tight and it came apart, which I've never had happen before. The cap fixed it. It was running good times again, but getting hot at the end of the 1/8. Avg CHT at 60 in the 1260s, which is too hot. 1300 or more by the time I was letting off around 70MPH or just under. I swapped to a 195 main jet from a 190 to see if that would cool it off. Really didn't seem to. Still 1300 at the end of the 1/8. It did go a little quicker though. Averaged 9.88 @ 67.25 which is on par with my best averages. At this point I'm thinking I've finally got it. Just need to cool it off at WOT a little and it seems like it may take a larger jet. Cruising to and from test spots it was in the 800-1000F range most of the time at 1/8-1/4 throttle so that was doing well. I'm on the home stretch! Well... I should know better. That's not how things go for me. I pulled onto the road toward my house and sped up to 68MPH before rolling out quickly. As I rolled out it was at 1299F EGT and it died. I let it coast, knowing that's less pushing if it doesn't start. Crossing fingers at that point. I came to a stop and hopped off to find very little resistance from the kick start. Oh boy. I pushed the rest of the way home, which thankfully was only about 1/2 mile or less. I did stop to check the kick start again, only to feel the same weak lever. The good news is, the dragy was still on so I know that I can do the 1/4 mile pushing my scoot in 269.86 @ 3.33MPH. I hit about 6MPH pushing at first, but I got tired. lol Haven't had time to look at it yet. I fear that I have installed a peephole into my piston. I can feel some resistance pushing the kick lever though. Could be the ring. I'll find out sooner or later.
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Post by aeroxbud on Dec 6, 2023 5:38:48 GMT -5
Oh dear. One minute on a high. The next the fickle scooter gods are punishing you for euphoria. Let's hope it's not too bad.
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