Compression Test, ~2,000 Mile Engine Checkup & Bringing My Scoot Back To Life! : TPR 86cc : Part 40 

I appreciate insight. Sometimes I wonder if comment makers have any idea what's going on, but this doesn't seem to be the case. You know, like telling me that the TPR won't last 1000 miles when I'm at near 2,000 stated many times in the video and title. I also thought detonation at first, but I believe it was Eric Gorr that talked about coolant leaks doing just this and actually leading to ring sticking in one of his publications. I don't claim to know the cause for sure, but the description that I recall about the coolant leak was almost exactly what I found. I did find a crack in my airbox (replaced) so maybe there was something going on? Normally, I hear detonation. I have never heard it with this kit. No sandpaper on the conrod. Just cloth and polish. The sandpaper was just to clean some rust off of the crank wheels. Kinda pointless since I can't get in there to clean everything, but I suppose it made me feel better. I do realize that there is a totally technically correct way to do things and then sometimes how things actually go. I didn't even measure the conrod small end diameter TBH, because I saw no signs of needle rollers eating in or anything of that nature that I've seen with other conrods. At this point, the head is either screwed because of the broken walls around the o-ring or it's will probably work OK. I could toss the whole thing (head and piston kit etc... would end up being near total replacement cost) or just see if I can get more use out of it first. The reason that I have not used a thread locker on my studs is that my initial experience with torque specs was with automotive cylinder heads. Most of which specify a lubricant, often motor oil or an overpriced specialty lube. These scoot manufacturers and aftermarkets don't bother, but I've been in the habit of using motor oil and generally it's not a big issue if I re-torque after heat cycling. I don't make any claims of being an expert and always correct. Thanks.

@@49ccscoot dont worry about torqing nuts on head/studs, just use coper washer under nuts and torq to the specific values. M6/M7 bolts and nuts 12~14nm. Never used locktite, just coper washers, never had a problem.

@@49ccscoot Don´t worry too much , the Tp thropy 70 ccm (castiron) in my vespa is already lasting near 45000km on the second piston.But my setup is very low rev on the ET2.(9gr rollers and sito plus exhaust) As long as you maintain it well it should keep going until a pistonring snaps or the engine runs dry.

Yeah, I'm concerned that it's going to leak again. Replacing the head and the piston would mean I might as well do the whole kit so I figured I might as well try it and hope it works for a while. Thanks.

Thanks. For me, by the time the head and piston kit were replaced, I might as well get a new cylinder kit totally. Figured I might as well try it and see what happens.

Thank you so much 😀

Wrong AMSOil. I used to use Saber Pro. Now I use Dominator. They did change their recommendations on Saber and that is when I switched over. Who knows, maybe I'll try something else after I go through a case and a half of this that I have. I've been pleased with it though.

I swapped out the ring at 1,000 miles because I had a spare on hand, but it had barely worn and didn't require replacement at that point.

Pretty much everything is 10% ethanol here, so I know there is ethanol. Could have had more water in a batch, but I still think coolant got into the cylinder.

Yeah. It felt wrong and sounded wrong, but lucky me I had no spark and no compression. Could have been worse though.

@@49ccscoot I know lucky the crankshaft was good after a clean tho . Tpr kit 1.8k miles is great for a hyper kit as you know

If you go back to my 1,000 mile checkup, you will see that it came apart coated in oil. There was no coolant leak at that point. Same oil. Same mix ratio.

I believe it was one of Eric Gorr's writings that talked about coolant leaking in and eroding the crown edges and leading to ring sticking. The rust and lack of oil residue on anything is a dead giveaway that coolant was surely in there... aside from the indications on the cylinder deck. Detonation will do something similar, but I'm not sure that's what it was in this case. It does seem odd that it would be around the edges so evenly with coolant that was likely coming from 1 to 2 points, but IIRC whatever I read about coolant leaks also eluded to a ring around the outer edge. I make no claim to be an engine failure diagnosis pro. I have not heard detonation yet. I've never not heard it before and found signs of it. Not saying that it isn't happening though.

Reduce the squish. A.G Bell recomends minimum of 0,6mm for 50cc

The ring will never reach the edge of the coating up top. If it does, I've got bigger problems. I'm just not used to coated cylinders and flaking can be an issue at rough edges. I'm hoping it's fine. Thanks.

I do a crisscross pattern.

Thanks. I'm using AMSOil Dominator Racing 2T pre-mixed at 32:1. It smokes quite a bit, but I know it's lubed.

Bookmark this page : www.49ccscoot.com/calculators.html There are calculators there for 2T and 4T piston rings and many other useful things. As long as you aren't planning to use a bunch of nitrous or anything too crazy, the gaps those calculators produce usually work well.

Super clean under the piston.

Compression test and making sure it has fuel would be next on the list.

Check out the forum. There are multiple LC conversions, some of which are Zumas.

1) You can install a BBK instead of repairing the existing top end. 2) 49ccscoot.proboards.com/thread/2556/wiring-diagrams & 49ccscoot.proboards.com/thread/340/manuals-documents

My belief is that it would likely be fine, if they hadn't machined the head a bit off center to make those 2 thin walls around 2 o-rings. The o-rings seemed to work well enough till whatever happened to those walls.

I flushed it. It's not ideal. As said in the video, I don't like the idea of any sort of abrasives being in the crankcase. Technically correct would be to disassemble the whole thing.

Also, I love the sound effects!

My opinion is that the failure would not be likely if the bore and stud o-ring spacing was more even. 2 o-ring grooves were closer to the bore than the other 2. Those 2 with thin walls are what failed. If your kit is in the box, look it over. If never used and you have the same issue, then maybe you can get the head replaced. Could be something that happened in one head or batch of heads and never again. I always advise people to do their own cases. I don't think it's worth it to ship them back and forth and I don't really like taking the risk that I ruin someone's cases. I'm not a confident machinist and it stresses me out. I did all of mine with flap wheels or carbide burrs till recently.

@@49ccscoot I'll get a look. And I totally understand where you're coming from. You did a great job on your cases but I understand. People think that I'm good with computers but I'm not. I'll work on mine and sometimes things work out. I'm definitely not going to touch anyone else's. I'm a member of the forum and I'll try to get some documentation of my build there.

If you go back to my 1,000 mile checkup video, you'll see that it came apart coated in oil. There was no coolant leak then. Same oil. Same mix ratio (32:1).

I know. I think anyone that doesn't do videos like this would probably be surprised just how much time it takes from adding a bunch of time to the actual work playing with cameras to editing and all of that. The big channels have a crew to film and edit and so on. It ain't like that here. It's just me. I'm literally hoping to get back to the SSR today, but it will be a longer process to get the next vid out for it because I have to work on something, then see how that goes so I can research and order other stuff and I'm at a part that to me is the most difficult of it. It's not forgotten.

I like to see ~150psi anyway, but if building to a spec I would use corrected compression ratio and aim for 7-8:1 for a street scoot.

Most likely your compression tester is not working properly and/or not sealing. Borrow another one if possible and try it.

0.9mm (TPR's recommended squish).

@@49ccscoot that's very conservative, fine for low power long life road bikes, and for manufacturer's butt covering. I ran 0.7mm on a 64x52 (bigger piston, more rod stretch) on your engine i'd aim for 0.6mm and only back off if the piston kisses the head while off throttle at high RPM.

@@TerraRoot It was 1.1mm. I had to shave the head to get it to their spec. I've stuck with it there because this is a road scoot, whether it should be or not.

@@49ccscoot full disclosure i'm a tiny bit of an armchair warrior having only tuned up two 2t engines, but everything i've read (mostly wayne wright's contributions) indicates 0.8 is the absolute maximum. i know you had detonation probably more from the coolant leak effecting the octane than the size for your squish, but if the squish was tighter the detonation wouldn't have been there in the squish area.

I think it is because of the broken o-ring grooves in the head allowing coolant into the cylinder.

The GP is very mild, like 8500RPM. I don't know much about the DR 70. TT is likely better, but you may want to check out Yasuni exhausts. They have a great reputation for performance and offer pipes like the Z and R for lower revving setups and the C16 is really popular for a bit higher revving stuff and makes great power.

Thanks :)

The DR 70cc is basically rebadged Top Performance black trophy cast iron 70cc

@@Sensey9383 I would think maybe the Yasuni Z, but a LeoVince TT would be OK too.

I have since day 1.

go to #11

Could be a quality issue, but also may be tuning. It could be running lean and soft seizing. It could be that it needs time running easy to break-in because of tight clearances.

Okay what cylinder kit performs just as good or better then the tpr with more reliability?

RU-vid should automatically create English subtitles. Then it can be automatically translated. It may not happen immediately and I don't know if they do Polish or not.

stage 6 to śmieci

Compression will vary. I saw one service manual specify 198psi for a stock 1E40QMB, which is ridiculous. I would really like to see 120-150psi for something like that. There's a lot of room for error with testers and sealing too. 84psi cold does not sound like something that should be running great. If possible, see if you can try another tester if you've got friends with more or maybe even a loaner tool from a parts store just to see if it changes. Sometimes I've had better luck removing the rubber ring and using the washer from a spark plug on the tester's fitting. Engine longevity will vary. There are stock Yamahas with over 20,000 miles on them. Nothing that I own is going to do that because it will be modified and ran hard, but it is possible. 70cc is fine with a stock crank, up to a certain point. Sport kits work very well for many miles with stock cranks in my experience. When RPM gets elevated, then it may be a problem.

@@49ccscoot thanks for this info :D now i care less about the connecting rod. and yes when it is cold it does not stay on the idle.