Compression test on '08 WR450F ?


3 replies to this topic
  • WR450FGreg

Posted September 28, 2009 - 02:44 AM

#1

.
Guys,

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.

Cheers,
Greg

  • SXP

Posted September 28, 2009 - 05:39 AM

#2

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.

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  • WR450FGreg

Posted September 28, 2009 - 11:29 AM

#3

.

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!

Cheers,
Greg

  • WR450FGreg

Posted October 08, 2009 - 11:13 PM

#4

.
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?

Cheers,
Greg

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