Pro-70 BX engine compression..

[dj_sparky]

I was wondering, how are the compression generally on these engines? I bought all new parts, except for the cylinder, and it still leaks a tiny bit of air out of the exhaust port. Is it supposed to do that or what? Or do I need to buy a new cylinder as well?

 

[Mickstix]

I "think" there usually around 60 psi. (just what I read) I doubt air leaking to the exhaust is compression related, but I could be wrong. lol.. How's that for a wishy-washy opinion!

 

[dj_sparky]

I hear a wheezing sound as air/nitro is pouring slowly out of the chamber (When I push the piston upwards.), in the exhaust port. Pipe isn't connected of course, so I can see directly into the "chamber" with the cylinder/piston. I can see the bubbles/nitro slowly leak when I push it.

Either it was the cylinder that was the source of the compression leak all the time, or it just leaks. It's pretty much brand new except for the cylinder at this point. I wouldn't even have asked this question for a .36< engine (Because then it would have been a problem, obviously.), but I could imagine that the larger engines have a slight compression leak...

 

[phx123]

When you say you bought all new parts did you buy a new piston with out a sleeve ? I'm not sure how the .70 parts come but usually piston and sleeve come together as they wear out together . Putting a new piston and an old sleeve together is gonna wear out pretty quick I think . That is my oppinion anyways . I'm sure someone with more experience will chime in .

 

[2revo1maxx]

I've always heard a little air getting past the piston on any engine I've owned, I'm gonna call it normal.....as long as it's only a little bit.

 

[Metalhead Matt]

I'd run it. It'll probably seat up after a couple of cycles.

 

[dj_sparky]

Well, I can hear "some" air getting out on most engines, if I put my ear up close to the exhaust gate. I assume "some" air gets pushed down/sideways instead of up along with the piston. But I can hear this clearly. Maybe it's cause of the size and it just does this, or the sleeve is leaky.

I'm gonna order me a new sleeve as well, since I spent a bit of money on the new piston/piston spring (Only on larger pistons.), and O-ring. Might as well be on the safe side and just replace everything before I try to start it.