how do you know if you have a bad piston or sleeve???

[Dreaux]

it still has good compression when the glow plug is in. But should i still feel a pinch when it is out???? The reason i ask is because when i take the buggy of the starter box and blip it around it will die suddenly does not really matter if if i turn it rich or lean. Hot or cold it has been doing this lately. i think maybe my engine is still to rich and it is loading up with fuel

 

[olds97_lss]

You should probably feel something with the GP out, but some run even if you don't.

I have an old TRX2.5 that has almost no compression and you surely can't feel any pinch with the GP out, but it will run all day long with decent temps in my jato.

Tear the engine down, take the piston/sleeve and see if you can gently push the piston through the top of the sleeve from the bottom. If it comes through the top, it's really worn and a $25 pinch may give you back some time.

Take a look at this thread to see what I mean:
https://www.rcnitrotalk.com/forum/showthread.php?t=56420&highlight=pinch

In the first photo, the two lower piston/sleeve combo's are worn enough to let me push the piston through the top a few mm. Both engines were having symptoms similar to yours.

 

[Dreaux]

no but it comes to about a quater inch from the top. I must tell you, this is a new os vspec. My break in process was fine but some things happened where i kept getting water in my engine and i would break it down. The first time i broke it down i just about drowned the engine in wd 40 and after run oil. ran like poop. Had to break it down and clean it again. Got water in it again, thats 2 times. Broke it down flushed it. And finally got it tuned right. now it want's to die on me.

 

[olds97_lss]

Quarter inch from the top with it apart or still in the engine? You can only tell if you actually take it apart and push the piston up by hand outside the engine.

 

[Dreaux]

i would have to check again but it's about a quater inch with the piston and sleeve outside of the engine in my hand. I already checked it.

 

[olds97_lss]

Then it must be the fuel or tune.

 

[Dreaux]

well how far from the top would you say it would have to be to be bad??? a eigth a sixteenth??? three sixteenths??? sorry i am a pipefitter.

 

[olds97_lss]

Don't know. All I know is that the engines I had that have your symptoms and more, the piston would push beyond flush with the sleeve.

Can you see wear marks inside the sleeve where the piston goes to top dead center? Can you push beyond that line very easily?