Compression test on '08 WR450F ?

3 replies to this topic
  • WR450FGreg

Posted September 28, 2009 - 02:44 AM



Is a compression test, similar to that done on cars, a viable engine top-end condition check on a WR450F?

If so, what compression should one expect? With engine warm or cold?

I've looked in the Owners Manual and can't find any actual figure in this regard.

For the record, yes, I do keep track of the km between oil/filter change intervals, etc. , even the conditions I ride in .... believe it or not.
I am very anal when it comes to record keeping with my bikes!

I just want to find out if people do compression checks and what they look for.


  • SXP

Posted September 28, 2009 - 05:39 AM


The auto-decomp setup on the exhaust cam makes this a pretty meaningless test. What you really want to do is a leak-down test. That should give you a pretty good indication of the condition of your valves and rings.

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • WR450FGreg

Posted September 28, 2009 - 11:29 AM



The auto-decomp setup on the exhaust cam makes this a pretty meaningless test.

Thanks SXP, I hadn't even thought about that, you are right!

I'll look into a leakdown test. I've been meaning to set up for them for quite a while now to check my 2 stroke TZ roadracers.
Now I have the perfect excuse to force me to get it done!


  • WR450FGreg

Posted October 08, 2009 - 11:13 PM


Ok, got my leak-down test kit, now what?
I've never used one before and it didn't come with instructions.

At the risk of sounding completely dumb.......
I guess I need to:
a) make sure the engine is at TDC on the compression stroke
:busted: pump air into it and monitor how quickly it leaks out

(My bike is an '08 WR450F.)
How much pressure?
How do I determine that a leak is (for example) rings and not valve guides?
How do I test crank seals?
How quickly should the pressure drop? By how much?


Posted Image


Join Our Community!

Even if you don't want to post, registered members get access to tools that make finding & following the good stuff easier.

If you enjoyed reading about "" here in the ThumperTalk archive, you'll LOVE our community. Come join ThumperTalk today!

The views and opinions expressed on this page are strictly those of the author, and have not been reviewed or approved by ThumperTalk.