PROBLEM WITH RC ENGINE.
 

So i was cleaning out the engine that i had just bought off a guy on this site. The engine seem to flow very smoothly and with out any problem. I took out the sleeve and Pistion to make sure there was no damage and put it all back together. The problem that i am having is when hits dead top center there seems to be slack. The rod seems to click before the piston goes back down. Is this normal or should the engine be flowing smoothing through the whole process. It does it will the head on, with the head off or will glow plug in.

PLEASEHELP.......

THANKS

RE: PROBLEM WITH RC ENGINE.
 

if you tried the same thing on 10 other engines ,new or used it would react the same way.
it is just the piston stopping while the crank is passing the TDC .
all my engines do the same thing.

RE: PROBLEM WITH RC ENGINE.
 

I'm guessing what you mean is that the engine didn't have this "click" before you took out the piston and liner. The first thing that's come to mind is to wonder if you put the piston and rod back the same way it came out. The rod only fits one way because there's a tiny chamfer inside one end of the bush and this chamfer has to face the crankshaft to give a clearance for the radius ground on the crankpin. If the rod's in the wrong way then the piston will also be in the wrong way round for the way it's been run in. This may be giving some extra pinch causing the click which is just the clearance in the rod bushes changing from one side to the other.

RE: PROBLEM WITH RC ENGINE.
 

Thanks you. big dog. I guess i just did not realize it when i was cleaning and rebuilding my other engines lol. I checked out one of my TRX 3.3's and it does the same thing. It must just get smoother over time.

RE: PROBLEM WITH RC ENGINE.
 

yes....thats the mechanical pinch that new engines have...once ran and broke in etc....it goes away.

RE: PROBLEM WITH RC ENGINE.
 

That "click" you hear with the piston at TDC is normal. Even well broke-in engines will do it. With the top of the cylinder being narrower than the bottom, the piston sticks a little bit and when the conrod switches sides there's a little "dead spot" where the piston doesnt move and thats where the click comes from. My car and airplane engines all do it. If you dont know how much fuel has been in the engine, I'd check the crankpin/conrod for excessive play.

RE: PROBLEM WITH RC ENGINE.
 

no problem