Yamaha G2 Blow By

[fixedblade]

I've read and searched on this site for the cause of blow by into air box.

No. 1 ~ Overfilled with oil, not the case with mine.
N0. 2 ~ Lifted cart, possibility yes (6" lift)
N0. 3 ~ Governor adjusted for high rpm, not the case with mine.
No. 4 ~ Worn out motor, not the case fresh engine rebuild, blew oil prior to rebuild as well.
No. 5 ~ Return oil tube plugged fro top of head to crank case, checked not plugged or kinked.

My blow by seems very heavy. I've read about bypassing the air box and installing a catch can for the oil. I would rather not do this. Would really like to figure out why. The only reasoning is the 6" lift.

Any suggestions??

Thanks!

[Mr. Mike]

When changing the oil are you only adding 1 quart of oil? That's all it holds and with a lift kit the dipstick will only read about half way with 1 quart. It's because the lift cause the engine to be on an angle which in turn causes a less reading on the dipstick. So if you're putting more than 1 quart in the engine because of the dipstick reading then more than likely that's what's causing oil to get into the air breather.

[fixedblade]

Yes 1 quart of oil. Dipstick reads 1/2 full with 1 quart with a 6" lift.

[Mr. Mike]

Then I got nothing. When you rebuilt did you replace the crank seals? Something causing excessive case pressure.

[G1-G9]

I had the same problem after I rebuilt an engine that smoked bad. I took the muffler off and the smoke stopped. I put a different muffler on that i had and problem was all gone. The old muffler just had so much oil in it that you would have thought the cart still needed rings. Just try running it without the muffler and see what happen's.

[G1-G9]

P.S. Never trust Mr. Mike.

[Mr. Mike]

Originally Posted by G1-G9

P.S. Never trust Mr. Mike.

He's right! I don't even trust myself.

[stuff4mason]

Mike's initial thought was dead on though!! The man has come a long way tommy!!!

[fixedblade]

Yes crank seals were replace. Thanks responses!

[smokindawg]

When you did the rebuild did you check that the cylinder was round and in spec? Or did you have it bored?

Did you replace the pistons and rings during the rebuild or just rings? If it were me (Since you've checked all the other things) I'd do a leak down test and see what you get. You may have an engine with an out of round cylinder, or may have accidentally damaged a ring on install.

A compression test is ok but it won't tell you the same thing about the engine as the leak down test will. Plus if you do have excessive leak down you can then tell if it's past a valve or the rings.