How do I do a compression test on my 06 yz450

I've searched but couldnt find nada, how do i block off the auto decompression??

u can't do a compression test there is no way to kik the motor over with out the compression relses u have to do a leak down test

thanks guys, my bike is ticking and now smokes out of the breather tube!!! :ride:;)

its white smoke kind of looks like water vapor something. but you can also smell burnt oil when your around the bike

i think its worn valve seals letting oil into the combustion chamber. and a faulty head gasket that lets water into the system (produces the white smoke)

If you have water/coolant in your oil, the oil will take on a distinctly milky/foamy look (visualize an oatmeal milkshake).

Oil that gets into the combustion chamber will produce smoke out the exhaust, not the breather. Oil, and for that matter, smoke (as distinct from steam), out the breather indicates combustion blow by in the crankcase, or simply too much oil in the sump. If it's blow by, it indicates a problem with the rings.

my oil is has never shown evidence of water contamination thats whats so strange but my coolant levels are always going down so it seems that it sucking water into the combustion chamber

That's a possibility, but not related to the blow by/breather thing. If you coolant level levels off around the top of the radiator tubes, that's pretty normal behavior.

If it's blow by, it indicates a problem with the rings.

What exactly is blow by? Oil from the combustion chmbr gets into the valve head and out the breather?

If you coolant level levels off around the top of the radiator tubes, that's pretty normal behavior.

Unfortunately it is quite a bit down. Like a quarter gone, to the point where it makes the bike run hot, I was out at Perris yesterday and it ran pretty hot I wasn't sure why until I saw how low it was.

What exactly is blow by? Oil from the combustion chmbr gets into the valve head and out the breather?
No, blow by is combustion gases getting past the rings and into the crankcase. The hot gases burns the oil off the cylinder walls and increases crankcase pressures and the net outflow through the breather.

If this suddenly appeared, and your oil level is in fact normal or below, you could have a scored cylinder.

back to the coolent problem if the coolent is leaking into the engine it will either contaminate the oil or have white smoke out of the exaust u may also want to check your radiator cap for the propor presure and that the seal is in good shape

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now