Hi Everyone,

I have a z950, pulled the back half apart to make sure everything was tight, wanted to start it with the vent tube pulled to check blow by, is this amount normal? It is small puffs of air at idle, tried to show by putting a microfiber in front of it. Should there be nothing blowing out or is this normal?

Thanks in advance.

[2015 Z Force 800 53/Trail EPS]

Blowby is what gets by the rings during compression and detonation..and a little up the exhaust valve guides. There will always be some. On a tight engine with minimal blowby, the piston's movement in the bore will cause a pulsing effect with the leakage making the out-flow slightly more then the inflow. This action is amplified with the increase in cylinders but the pulsing is still prominent. Put your finger over the end and allow the weight of your finger to rest against it. Normal would be your finger bouncing on and off the end of the vent tube with little to no sign of vapors or smoke. If your finger is blown away from the end all the time, that is more then normal and if your finger gets wet with oil vapor, consider it excessive. In either case one would want to do a leak-down test to access the condition of the rings.