Leakdown test help

Hi guys, wondering if you could help me out on a leakdown test on a 2008 450 SX-F. I just got the bike and it runs pretty good but I just wanted to check the valve lash and figured I'd do a leakdown since I am already in there.

I have the valve cover off

Cams are pointing in opposite directions with the holes lined with the top of the head
I used a modified M8 bolt to hold the crank in position
I hook the leakdown test up and am getting about 70% blow-by which is impossible (bike runs well), I spun the assembly around once more to make sure i was on the compression stroke and same thing.

Any ideas of what I am not doing correctly? It sounds like its blowing into the case, I can't hear anything coming out of the carb or exhaust.

was the engine at temp when you did the leakdown...


We only have a compression ring, so dont expect awesome numbers

No it wasn't, I will warm it up and try again thanks. Should it also be warm for a compression test? What numbers should I be looking for on a compression test? I have searched a couple forums and read different numbers?

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