2010 yzf 450 86 hours time for new piston?

3 replies to this topic

Posted February 09, 2014 - 12:56 AM


how many hours are you guys runnin your first piston for? my bike is starting good valves ok heaps of compression.but dont want to run her in premature death.but i dont want to give her a new hart if i dont have to yet.... cheers yzf mad....

  • SAthump

Posted February 09, 2014 - 07:29 AM


Change your timing chain

If your valves are good & leak down test has good numbers go another hundred hrs and repeat.

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  • NitrousR1

Posted February 09, 2014 - 10:32 AM


Personally and professionally I always recommend replacing the piston and pin at 80 hours. At 80 hours of hard riding my rings are out of spec. The piston measures at the lower end of spec as well. For a lighter riding style you probably could go to 100-120 hours but I don't think its worth it. Spend $200 now for a piston or $2000 later If it blows.
Timing chains I always recommend replacing every 30 hours. You would be surprised how they stretch in those 30 hours. The chain is only $20 anyways and cheap insurance. I've been selling them at every valve adjustment.
With those maintenance items you will get many more hours out of your Yz. Enjoy it!

  • grayracer513

Posted February 10, 2014 - 07:44 AM


Whether the chain "stretches" or not (it wears at the pins, in fact, doesn't actually stretch) depends more on your oil and oil change habits than much of anything else.  None of mine have been significantly longer overall than the new one.  Changing them annually is a good idea, anyway, and cheap insurance. 


The piston depends a lot on what kind of riding you really do, and on how exactly you ride.  A bike that is raced in MX regularly, or generally just really ridden hard should have the piston replaced at "around" 80.  Mine went just over 300, but I ride desert races, so the bike spends a lot of time running at lower RPM's and less than full throttle loads overall than an MX bike.  300 was a little longer than it should have been run, too, as the ring land area of the piston was beginning to contact the bore walls. 


Another area of concern is the ring grooves.  These tend to wear wider at the outside of the groove than near the bottom of it, and after a while, the rings will start to twist at TDC/BDC as they reverse direction.  That leads to the rings "digging" little shadows at the top and bottom of the bore.  Small as these are, they can be the reason that a cylinder needs to be replaced or re-plated.


Physical/visual inspection is the best way to answer your own question. 

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