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Post by 190mech on Jul 19, 2024 15:55:03 GMT -5
Brent , Have you seen the recent replies (39629,39633) at KiwiBiker about the Polini PWK? Seems they have some 4 stroke parts mingled inside..
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Post by Lucass2T on Jul 19, 2024 17:08:17 GMT -5
Brent , Have you seen the recent replies (39629,39633) at KiwiBiker about the Polini PWK? Seems they have some 4 stroke parts mingled inside.. Oh geez... But that would make it run horrible if that really happened. Dellorto has a 2t and 4t version of the PHBG and if you swap the 2t and 4t specific jets and tubes around you'll instantly know theres something going on. |
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Post by 90GTVert on Jul 19, 2024 18:35:29 GMT -5
Brent , Have you seen the recent replies (39629,39633) at KiwiBiker about the Polini PWK? Seems they have some 4 stroke parts mingled inside.. I hadn't looked for a bit because they were kind of done with my issue for now. I just went and read and replied there. Thanks John! |
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Post by 190mech on Jul 20, 2024 3:28:00 GMT -5
I saw your pic of BDC port mismatch, WOW that is a lot! How can that be, the port map you posted a few pages back showed all ports at 45mm at BDC?
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Post by 90GTVert on Jul 21, 2024 14:41:28 GMT -5
I saw your pic of BDC port mismatch, WOW that is a lot! How can that be, the port map you posted a few pages back showed all ports at 45mm at BDC? I went back and took that out. That was from when I first was looking over the RC1 when I got it and not with the cylinder installed. Not what the ports actually look like @ BDC. TBH I don't know what the hell I was thinking when I posted that. The real setup will put the port floors below the crown. With the thicker gaskets it's close. I'll check again when I put this kit on. |
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Post by luvscooters on Jul 22, 2024 5:07:33 GMT -5
That's a lot of copper high temp gasket sealer used on that head in their first picture. It's way too much it's gooped on and being squeezed out
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Post by 90GTVert on Jul 22, 2024 5:55:57 GMT -5
That's a lot of copper high temp gasket sealer used on that head in their first picture. It's way too much it's gooped on and being squeezed out LOL No doubt. That was 15 years ago. I was spending too much time on V8s where you put a bead here or a little glob where this meets. Live and learn. Now I'd just use copper spray on an AC head gasket and other gaskets get smeared thin if coated. I'm sure you can go through this thread and see that I have and continue to learn a lot the hard way. 😵 The worst is learning, forgetting and learning again that way. LOL |
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Post by 90GTVert on Jul 24, 2024 13:57:09 GMT -5
The piston is actually above the transfers at BDC. I had it stuck in my head that it was the other way around for some reason. Anyway, I normally use something like a 0.2 or 0.3mm gasket to get squish right with the past cylinder kits and just leave the transfers as they are. At this point, I've got a new head, one that's in good shape and one that is now beat up a bit from the circlip. Might as well try some stuff. I put 0.7mm worth of aluminum gaskets under the cylinder (2x 0.3mm and 1x 0.1mm) to get the transfers flush. That ruins squish, which is supposed to be 0.55-0.6mm. I had 1.08mm. The combustion chamber is recessed roughly 0.5mm. Initially I tried to leave just a tiny bit of that recess, all but cutting it out. I figured maybe it's more of a firewall for the o-ring if it's not level with the rest of the head? Didn't matter. O.66mm squish clearance. Then I cut it flat. 0.57mm minimum squish. That'll work! So I cut off 0.51mm based on the squish. I'm never 100% sure on the mini lathe because of rigidity. I had to make more cuts because I was afraid the outer section would contact the cylinder and I had made the o-ring groove more shallow. Hopefully it can seal now.   It's not put together just yet. I was considering looking for 0.7mm aluminum to make a single gasket, but I may just use 3. Not generally a fan of stacking, but I've got to seal both air/fuel and coolant and I'm thinking maybe the 3 more malleable gaskets are better with light sealant on each. It's also easier and cheaper ATM. If it's a fail, I've still got a new head and can go back to the usual squish setting gasket choice. I'm hoping maybe it will cool the piston slightly better if nothing else, but don't really think it will make much difference. With a degree wheel, I got 198 ex / 132 xfer. One thing that would be amazing is a portmap with these dilensions 1.Btdc heigth in the bore 2.width and heigth of all ports at 3 diferent points 3.distance from exhaust port top to a transfer ports top 4.width of the bridges between ports With these you can analyze the engine in very precise detail. Also port pos/dir/axial parametres are important Maybe this will be of some use? Hope it's understandable. With the port measurement map, r is radius of a circle that matches the corners and H is height of the port.    Exhaust roof : 6° Downswept Exhaust floor : 9° Downswept A transfer roof : 25° Upswept B transfer roof : 19° Upswept Large boost roof : 55° Upswept Small boost roof : 40° Upswept |
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tysta
Scoot Member
Posts: 79
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Post by tysta on Jul 26, 2024 2:32:47 GMT -5
So 1st thing if you have been running less than 0.8 of squish that's why you keep detonating or seizing the piston too much heat. You will need to run at least 0.8.
Also if you have the squish at less than 0.8 I don't see that cylinder having 198ex need to be less.
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Post by 90GTVert on Jul 26, 2024 5:59:23 GMT -5
I've been going by Malossi's spec since day 1. Never had a problem at 0.55-0.6mm squish clearance for all the miles before the carb. Only difference now is that the transfers are flush instead of below the crown and duration is up IIRC 2 degrees from the first time I checked when I originally assembled the RC-1. I'd think if I were worried about compression, I'd be better off to enlarge the chamber and leave tight squish for detonation resistance. Again though, if that's a problem it would have to be one of those deals where it was fine till the big carb changed something.
I just put it together yesterday. I used Ultra Grey on all 3 gaskets, thin, and stuck them together before putting them on the engine to get them aligned. Put the cylinder on (after going at both circlips with a pick to check) and let it sit snugged for an hour, then torqued to spec. Gonna go leak test in a minute. Changes since last time riding are now port matched intake, raised cylinder, more conservative timing curve, drilled fuel passages in carb, plus detonation gauge. More than I like to change at once, but this piston eating needs to end.
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tysta
Scoot Member
Posts: 79
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Post by tysta on Jul 27, 2024 0:33:15 GMT -5
I've been going by Malossi's spec since day 1. Never had a problem at 0.55-0.6mm squish clearance for all the miles before the carb. Only difference now is that the transfers are flush instead of below the crown and duration is up IIRC 2 degrees from the first time I checked when I originally assembled the RC-1. I'd think if I were worried about compression, I'd be better off to enlarge the chamber and leave tight squish for detonation resistance. Again though, if that's a problem it would have to be one of those deals where it was fine till the big carb changed something. I just put it together yesterday. I used Ultra Grey on all 3 gaskets, thin, and stuck them together before putting them on the engine to get them aligned. Put the cylinder on (after going at both circlips with a pick to check) and let it sit snugged for an hour, then torqued to spec. Gonna go leak test in a minute. Changes since last time riding are now port matched intake, raised cylinder, more conservative timing curve, drilled fuel passages in carb, plus detonation gauge. More than I like to change at once, but this piston eating needs to end. With all do respect but Iam doing this for almost 30 years at this point what do I know?!!! Right. Like I mentioned before fuel in Europe is completely different how I know well I lived there for almost all my life. Did you ever measured the combustion volume? Did you ever measure the squish band?!! 8.1 have the best engine out there and their head also have mistakes and it can be improved. After reading you were using that tight of squish on 98cc engine and seeing the failure you been having and the hard time to adjust the engine it says it all Move that squish to at least 0.75 set the ignition correctly and I bet with you the stock jets even on a 33 mm carb will work right of the back and you be way more easy to tune. One the problems you have is the temp sensor and egt sensor you are using will not react fast enough for you to see the problem! |
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Post by 90GTVert on Jul 27, 2024 20:07:02 GMT -5
With all do respect but Iam doing this for almost 30 years at this point what do I know?!!! Right. I'm not saying I know better or that I'm not listening. It's just that regardless of experience, I don't trust anyone's observation over my own as far as what worked for me. This setup absolutely worked with just routine maintenance piston swaps due to mileage till the PWK. That's from ~2 years of my own experience with a ton of dragy runs, video, etc... with this engine so I know it worked for sure and I was once impressed with how reliable it was. Did you ever measured the combustion volume? Did you ever measure the squish band?!! No. I've basically trusted Malossi there, because again it has been so reliable till the PWK. I've done it a bunch of times with other engines, but that was because I was trying to figure out what they needed to work and this was just a stock RC-1 so I didn't question it. Not saying it's the best ever, but it worked for me and I left well enough alone. After reading you were using that tight of squish on 98cc engine and seeing the failure you been having and the hard time to adjust the engine it says it all How does that coincide with 2 years of reliable operation though (aside from fuel supply issues at one point and the floats in the VHST getting heavy and needing replacement)? The VHST seemed to work well with a fairly wide range of jetting and was never a problem to tune (when no underlying issues were present). Move that squish to at least 0.75 set the ignition correctly and I bet with you the stock jets even on a 33 mm carb will work right of the back and you be way more easy to tune. This Polini carb had a 122 MJ from the factory. I don't know that I'd bet on that being the right choice. One the problems you have is the temp sensor and egt sensor you are using will not react fast enough for you to see the problem! I don't disagree there. The probe is 350ms response time. From the same supplier, there is a 150ms version. Basically mine has a shielding, which I figured would be good for a 2T real street environment, and the other is the bare sensor for lack of a better description. Naturally those have to take a totally different bung than what I put in my exhausts. I don't think I'd react quickly enough to make use of 0.15 seconds vs 0.35 seconds. Human visual response time is roughly 0.25 seconds, but I guess one still puts you 0.2 seconds ahead in a perfect world. Not sure on the update rate of the Koso gauge. That's where the detonation gauge was supposed to help some. The problem is, it has never worked for me... So I took my first test ride yesterday morning. Just tooled around at 1/8-1/4 throttle for a half hour or so to let it break in easy. The knock gauge was only on with the one green light to indicate that it has power. Looks like it's supposed to have the next 1-2 green lights coming on just from regular engine noise... but they weren't. I pulled over and turned the sensitivity knob and it never made the lights come on. It did then basically free spin and feel loose in the case. When I got home I looked it over and unplugged and replugged the sensor and it won't respond to tapping on the sensor or anything. I'm not terribly impressed with the quality of this knock gauge. I'm assuming the potentiometer, or whatever it is for sensitivity, is bad or disconnected now. I would have to pry the 3M double sided tape off to get to the screws on the box to take a look, but I decided to just do a few test runs after it cooled and look at the gauge later. I got to 57MPH in the first run and it died. Felt like no compression. EGT was 1222 when it died, and what I usually see for best results has been 1200-1250 at 60MPH... so pretty much right on par with where a good pass should be. I'd never worry and shut it down at that point.  Aftermath :     This is a different plug than I normally use. It's the Malossi specified Denso IW34, which is cold and fouls easily for street riding in towns and such. I normally use NGK BR10EG or BR9EG... and I think the IW34 is something like an 11 NGK. This plug was in there for the break-in ride, again at 1/8-1/4 throttle. Still, the mixture ring isn't one that makes me think way lean, destruction in a matter of seconds is imminent. 
So, I thought this would be safer than any past runs. -More conservative timing -Drilled fuel passages in carb for faster bowl filling (not an issue based on GoPro observation, but can't hurt) -Colder plug -Port matched intake to carb -Piston crown flush with transfers @ BDC (hoping for any extra cooling of the crown) I did switch it to a 200 Keihin main jet, though it ran strong with 215 and 220 Niche Cycle jets last go-round. The reason is that flow numbers for the 200 Keihin (my tests, who knows how useful) showed the 200 Keihin to move as much fuel as the 215-220 NC jets. Could be that that bit me in the ass, but look at the mix ring and look where the EGT was compared to expectation at that point and it doesn't seem like it should be mega-lean. Plus, I could get away with up to 1400 EGT when I first started out with the PWK and everyone else's jetting range and it didn't die. This is the quickest it has ever done this. I thought it was safer than usual and it wound up being the worst ever. I was absolutely devastated after this happened yesterday. I know that's silly because it's just a scooter, but I've put a lot into trying to see why this damn thing won't be tuned and it's broke me (doesn't take much) and it's now worse than ever... and riding and scoots are my life. I stared off into space for a minute wondering why I'm even here and then for about an hour I contemplated never touching a scooter again. The truth is, if I had a pile of cash sitting around, I'd gladly throw kit after kit on it because I love trying to learn about stuff... but in the real world I sure don't have that cash pile. I've been limiting myself to 1 ride per week on the TMAX for a bit now just trying to save the money I'd spend on gas. 30 miles 2 weeks ago, 160 miles last week since a friend wanted to ride, 25 miles this week. That's nothing for me. I don't think the lack of enjoying anything is doing me much good and neither is feeling like I must be a contender for dumbest person in the world to struggle like this after 20 years of small bike tinkering. Clearly anyone other than me would have this tuned within an hour. Just venting. |
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sinfull
Scoot Enthusiast
Posts: 413
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Post by sinfull on Jul 27, 2024 20:41:42 GMT -5
You are not alone, I had to step away from 2 stroke engine after a similar destruction pattern developed. Kinda like a gambler running into a cold streak with the cards.
Taking a break and just enjoy your t max for awhile isn't being defeated or failing. You have one of the best step through scooters available, be happy and just ride for awhile.
T2 can sit and contemplate it's life choices 😆
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Post by aeroxbud on Jul 28, 2024 3:14:10 GMT -5
It won't display the pictures for me. But I'm guessing it's not good.
I really would just go back to the Dellorto you used before at this point. Or perhaps try one of the Dellorto carbs Lucass suggested.
I can understand your frustration. It would be driving me nuts too. But I think you have given the PWK a good shot.
Yes we would all love to know what's going on. But I would be moving on from this now.I
Go for a ride. Forget about T2 for a few weeks. Then come back to it when you feel up to it.
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sinfull
Scoot Enthusiast
Posts: 413
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Post by sinfull on Jul 28, 2024 4:32:26 GMT -5
Exactly Aero. Do something fun if you absolutely have to work on something. You said you liked the scooter your buddy did with the short frame and the elite panels.
With your talent and experience you can build anything you want. You enjoy making parts on your lathe and doing some fabrication. Then do that to something that is fun. Put your old mhr on a qmb and make it run, find the most clapped out meth rocket you can find and do it up right with what you have available or can order from temu.
Point is don't get discouraged. You are still a very good and thorough small engine technician. I would trust you to build a engine for me anytime.
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