350x blowing 'exhaust' out the oil filler

[jaykup]

So I just bought this 350x that I'm told had a new high compression piston in it. It seems to ride fine, but not as fast as I'd like, (only hit 55mph on it) so I go to check the oil. First, I pull the oil cap off while the engine is running, not to check, but just to see what happens. As soon as I do, its blowing out what feels like exhaust out of the oil filler hole, I didn't smell it, but its under quite some pressure.

Does this mean my rings are beyond shot? Is this hurting something on the lower end (probably gaskets hey)?

My guess is a high comp piston was put in at a standard size, with a worn cylinder.

Its a LOT of pressure though, and seems to run alright.

Any ideas?

[200xman]

That should just be crankcase pressure. Unlike a 2 stroke the piston in a 4 stroke is going up and down in the crankcase creating pressure. The 2 stroke piston is sealed from the transmission in order for it to function without valves. Basically any 4 stroke that you pull the oil fill out will have positive pressure.

[traxxasx]

So I just bought this 350x that I'm told had a new high compression piston in it. It seems to ride fine, but not as fast as I'd like, (only hit 55mph on it) so I go to check the oil. First, I pull the oil cap off while the engine is running, not to check, but just to see what happens. As soon as I do, its blowing out what feels like exhaust out of the oil filler hole, I didn't smell it, but its under quite some pressure.

Does this mean my rings are beyond shot? Is this hurting something on the lower end (probably gaskets hey)?

My guess is a high comp piston was put in at a standard size, with a worn cylinder.

Its a LOT of pressure though, and seems to run alright.

Any ideas?


I think its like a messed up vavle, my moms car did that when you take the oil cap off exhaust was comming out from it and it was pressurized, we took it in, broken vavle.

[leetwanker]

I think its like a messed up vavle, my moms car did that when you take the oil cap off exhaust was comming out from it and it was pressurized, we took it in, broken vavle.

Car engines and three wheeler engines are built very differently. When you unscrew the oil fill cap from a car, the valves ar right underneath that, so yes, if gasses are leaking past a valve in a car, exhaust might come out of the oil fill port.

On a threewheeler, the piston and rings are a barrier between the combustion chamber and the crankcase. Only if your rings are going could exhaust gasses be getting into your crankcase, which is possible, but I think the bike would be smoking like hell if that was the case.

[Russell 350X]

Does it have the power like it should? The pressure out of the filler hole is normal I belive, I don't know why it wouldnt be.

[jaykup]

alright, thanks, Its not smoking and it has full power through the revs.

I just raced a 2004 Kawasaki KFX 400 4 wheeler with one tooth down in the front, a UNI filter, jetted, and he only pulled 1 4 wheeler on me in the beginning, and i kept right up with him until 6th and I started to pull a little. It was a nice race.

Its got stock gearing though, so im going to go wtih a 14 in the front, with my 22x11.5x8 tires. He was supprised!