How to do a compression test on a 04 yz450f


3 replies to this topic
  • Blank Stare

Posted January 05, 2007 - 04:54 PM

#1

What do i need to do in steps? and what should the readings be?

  • grayracer513

Posted January 05, 2007 - 05:07 PM

#2

You can test in a couple of ways.

>With the AD system enabled: There are no cranking compression figures published that I know of, but it should generate roughly 100-120 within 5 compression cycles.

> With the AD disabled. Remove the cam cover, push the AD flyweight out to retract the decomp pin, and wedge a small piece of folded match book cover, business card, etc., in behind it so that it will stay there while the engine is turned over. You should see more like 190-210 this way within 5 kicks (it will be very hard to turn through, and this can be tough on the starter)

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  • Blank Stare

Posted January 05, 2007 - 05:30 PM

#3

You can test in a couple of ways.

>With the AD system enabled: There are no cranking compression figures published that I know of, but it should generate roughly 100-120 within 5 compression cycles.

> With the AD disabled. Remove the cam cover, push the AD flyweight out to retract the decomp pin, and wedge a small piece of folded match book cover, business card, etc., in behind it so that it will stay there while the engine is turned over. You should see more like 190-210 this way within 5 kicks (it will be very hard to turn through, and this can be tough on the starter)


thanks.
the only starter is my foot. I guess i should wear my riding boots when i do the AD disable method
Thanks again

  • grayracer513

Posted January 05, 2007 - 10:34 PM

#4

By starter, I meant the kick start gears and the crankcase. They have been broken before.

Getting a leak down test done will be more meaningful than a cranking compression test.





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