Seems the man who sold me the motor wasn't very truthful about the engine. Ran about 7 tanks through it at the OS break-in needle settings yesterday and today and the motor has lost nearly all compression.

So I need a pinch, not going to try and get my money back, buyer beware and all that.

Any hobby shops that do it? Anyone on the boards come with good reps? Otherwise I'm ready to buy a piston and a sleeve.

Motor runs way faster than the Force .26 even at break-in settings with the low compression, but its not where it should be.

NM, found the piston/sleeve brand new shipped from Tower for $70. Now its like having a new motor.

Ive heard that when an O.s. is broken in they dont have compression like other motors. They feel very loose. (Ask mike Czech, he has a vspec thats looser than a 70 year old hooker and that motor rips!)

Besides if you get a pistion and sleeve you should REALLY get a connecting rod and wrist pin as these to componets take the brunt of the load and may or maynot be up to the task of handling the rigors of yet another break in period. Which we all know is toughest on these parts...

Yeah, but so little compression that I can pull the pullstart with my pinkie?

That seems really loose.

Revise that, I can turn the flywheel over with my pinky. I can't do that to my OS .18CVR and thats a smaller motor.

My OS .18cv-r had no compression after break in, and it ran fine. Still does run fine according to MaxxGS.

with a motor this small and no piston ring to boot no compression by just spinning the flywheel doesn't seem that far off. If you turn the motor over faster it would have a chance to build compression (pull start, bump box, roto). Just simply turning the flywheel by hand isn't nearly fast enough to determine that (blow-by is to great at such a low speed). If I was you did verify everything else first.

I have I think 10 pinchers in sizes from .12 to .21 If I have one that fits you can use it

those little tools usually do more damage than good

Yeah, but it has no pinch, there is no compression it slides smoothly almost as easily as if I had the head button off. You should see the compression on my Jato. Its almost impossible to turn it over with just one finger turning the flywheel.

I've got two OS .12s of unknown usage with more compression. An OS .12CVR, and a .12TR.

os will run just as good or better with less pinch, even though it may not have mechanical pinch it still has compression most likely. Until your tune starts getting eratic or it wont idle then its time for a pinch until then just run it

It doesn't idle unless the idle speed is high enough to move the car at a few miles per hour.

Around 200* Full throttle runs just mean that it'll bog down like its too lean, but only at a very high RPM. Its not too lean though, and its not so rich as when its cold its fine. Tried a colder plug, but anytime it gets near 200* it will not idle at all.

I didn't start this thread so people could convince me that it does not need a pinch. I've already ordered the parts, they will be here tomoroow. No one who has pulled that pull cord thinks it has any compression.

When I met up with MaxxGS, he didn't like the compression on my CV-r after 1 and 3/4 of a gallon. Still plenty of power though.

The 18TM has great compression and sticks at the top after 2 gallons of abuse. My 21 RG's on the other hand had hardly any pinch after a couple gallons. One of which I'm on gallon four and the other made it to 12 gallons before I had OSRocket pinch it. I've run 3 gallons or so on it since then and it still gets stuck at TDC.

But, like you said, if it's starting to be hard to tune and to keep it at idle, it's probably time for a squeeze. Although, I'd suggest using OSRocket or rayaracing. They have the right tools to do it correctly.

If you have OSRocket do it and it's a pullstart engine, make sure to ask for a mild pinch... Trust me!

Well, I found the piston and sleeve for $70 shipped so I just ordered it. Though it would be about $150 but when I saw the piston/sleeve kit for $70 shipped I just bought it. I figure I can get my current sleeve pinched and then store it for safe keeping so I can swap it out when the new one gets worn out. I can replace bearings and seals at that time too.

It runs good but once it gets to a high RPM it just bogs out bad. Absolutely dies if keep on the throttle because the heat makes me loose all compression. Runs great so long as I'm not on the throttle for more than 5 or 6 seconds. Its not bogging on the top end because its too lean though. Steady stream of blue smoke out the exhaust at high speed and when I temp it its only about 200* to 210*

Got the full story from the seller. Turns out he's not the original owner, but rather bought it from a racer at the local track. So he really didn't know how much went through that motor or what care was put into it. Oh well. Good as new in a couple of days anyways.