2007 202 hrs


2 replies to this topic
  • SteveO yz450

Posted January 29, 2013 - 11:38 AM

#1

Hi Gray, and or anyone else
Looking for your opinion on my bike. 202 hrs on it, replaced the timing chain at 100 hrs and adjusted the valves, they were all within spec but one. Tore the bike open to do a top end last night and exhaust valves are in spec, right intake good, left intake a little tight, center zero clearance. at 202 hrs should I do a complete valve job? Also cylinder shows some ware, at the top and bottom of the stroke, should I replace cylinder? Have a complete top end kit, and new timing chain ready to go.

Thanks Steve O

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  • grayracer513

Posted January 29, 2013 - 01:45 PM

#2

You will need to measure the cylinder for wear to determine what's to be done with it. I recommend having this done by someone with a good bore gauge and experience in using it, as they are a challenge to use accurately, and the wear tolerance is only .002".

The center intakes always seem to go first, mostly because so much of the fuel goes through the center port, which washes that valve cleaner of oil and combustion wastes than the outer two. You'd think that would be a good thing, but it's that "goop" that keeps the outer two valves form wearing as fast. Here's the thing: There is no realistic way to know how much longer the other valves will last before they wear through their individual hard coat and start sinking fast.

The choice is essentially yours: Do the whole head and know what condition everything is in, which should give you another big pile of trouble-free hours to play with, or go the minimalist route, fixing only the center valve, and then have to do the others at some unknowable point in the future, a year from now, or maybe next month.

  • SteveO yz450

Posted January 29, 2013 - 06:31 PM

#3

You will need to measure the cylinder for wear to determine what's to be done with it. I recommend having this done by someone with a good bore gauge and experience in using it, as they are a challenge to use accurately, and the wear tolerance is only .002".

The center intakes always seem to go first, mostly because so much of the fuel goes through the center port, which washes that valve cleaner of oil and combustion wastes than the outer two. You'd think that would be a good thing, but it's that "goop" that keeps the outer two valves form wearing as fast. Here's the thing: There is no realistic way to know how much longer the other valves will last before they wear through their individual hard coat and start sinking fast.

The choice is essentially yours: Do the whole head and know what condition everything is in, which should give you another big pile of trouble-free hours to play with, or go the minimalist route, fixing only the center valve, and then have to do the others at some unknowable point in the future, a year from now, or maybe next month.


Thanks Gray
I ordered all new valves, springs, seals and a new cylinder. $660 with tax pick them up Thursday from the local shop. Already have the rest of the top end kit & chain. 202 hrs can't complain that's a lot of fun time.





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