tech ? compression

6 replies to this topic
  • dboy1k

Posted February 02, 2012 - 06:25 PM


On an 08 450 yzf what should the compression be?
I have 50 psi is that low?
I'm getting a lot of oil coming out of the side blow off tube at the bottom left.
Any thoughts?

  • grayracer513

Posted February 02, 2012 - 09:49 PM


That's a little low, yes, but with auto decompression, normal isn't lot higher. Check the valve timing, then have a leak down test done.

  • dboy1k

Posted February 03, 2012 - 06:59 AM


Well I pulled the top end last night and found that the 2 outer intake valves have a ton of build up on them almost the thickness of a popsicle stick!
I'm thinking this is what's been causing all my issues!!
Perhaps the valves are hanging up and not sealing.

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  • Gunner354

Posted February 04, 2012 - 08:12 AM


Can you please tell how many hours is on the motor, what jetting you have and what gas you use.
That carbon build up is easily removed when soaked in wd40.
Learned this trick from my wife's uncle who builds motors for various top fuel guys.

  • dboy1k

Posted February 05, 2012 - 07:53 AM


the bike had 37 hours when i got it and now it has 51.
i use a half 92 half 110 ratio on fuel
i believe it was alot of dirt on them.
the crazy thing is that it was only the outer ones. the inner one was clean as can be

  • Gunner354

Posted February 06, 2012 - 12:46 PM


What jetting and what pipe if any?

  • dboy1k

Posted February 06, 2012 - 07:19 PM


Full pro carbon white bros with 170 main 45 pilot
I pulled a Carb off a perfectly running same bike and it ran exactly the same
I'm 100% sure its not Carb,CDI,coil,head issues.
I ordered a stator today so we will see what happens next

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