08 yz450f rebuild

9 replies to this topic
  • rjcook450

Posted November 30, 2009 - 03:58 PM


I have an 08 yz450f. I'am a vet. rider, some may have seen my riding on youtube under profile name rjcook450. The bike has 71 hrs. on it, nothing has been done to it other than spark plug replacemnet, oil changed every 5 hrs., airfilter cleaned regularly, bearings greased every year, and I have checked the valves twice, once at 40 hrs. and just recently at 70 hrs. they havent moved. They are, both Exhaust .18, both outer intakes .10 middle intake .13.
I was trading the bike in on a 2010, but until I pay off wifes wolverine, I can not afford payments, so my question is what should be done as far as rebuild. The forks and shock are being serviced. With the motor I planned on timing chain and tensioner. The mechanic said he would do a leak down test to see what might need done, if it comes out good then are the piston and rings fine or should the head be pulled to look at cylinder, or should I just have them done anyways? Anything eles that I am missing that might need done?
Thanks. Jason

  • Wes Woodin

Posted November 30, 2009 - 05:08 PM


I would just rebuild the top end. Replace valve seats, timing chain, piston rings. Change oil and dismantle bike to grease all pivot points. New chain sprockets if the need it and lube all cables, change plug, m:thumbsup:aybe a new air filter. Bike will be like new and last a long time. You may want to change the oil in the front forks and rear shock.

  • ForsheeMS

Posted November 30, 2009 - 05:46 PM


At 70 hours I would replace piston, rings, valve springs, and timing chain. Clean the carbon off the combustion chamber and valves. A new set of valve stem seals would be a good idea too.

  • rjcook450

Posted November 30, 2009 - 05:57 PM


I'm leaning towards piston and rings, but will wait on valves until leak down test is done. I dont see any reason to tear into head if its not needed.

  • davcon

Posted December 01, 2009 - 07:02 AM



Personally, I'm going to hold off on the piston and rings. I replaced the timing chain as suggested.

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  • nephic

Posted December 01, 2009 - 07:31 AM


BOLD NEW GRAPHICS:banana::banghead::banana:

They always make me feel way faster.

  • rjcook450

Posted December 01, 2009 - 02:29 PM


yeah I got polisport ipd plastic on the way

  • FinchFan194

Posted December 01, 2009 - 03:49 PM


I say get your leak down test done and if it is fine then don't do anything to the motor. Spend your money on the suspension maybe have it revalved along with the service you are going to have done to it.

  • rjcook450

Posted December 02, 2009 - 02:48 PM


Yeah, good idea. Still will replace timing chain though. I will check into revalving suspension too.

  • FinchFan194

Posted December 02, 2009 - 03:05 PM


Good call on the timing chain. . .

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