100 Hrs on an 08 - What would you replace?


13 replies to this topic
  • davcon

Posted November 16, 2009 - 06:51 AM

#1

Mainly trail ridden by vet rider. Well maintained. Adjusted the valves twice but thats it. I ride out in the boonies where there is spotty cell service and would not want to push it back to the main road(s). Want to keep it reliable. What would you replace? Thanks!

  • grayracer513

Posted November 16, 2009 - 08:18 AM

#2

The timing chain absolutely.

How much total valve adjustment has been done? Two adjustments in 100 hours seems a bit excessive.

  • l_campionero

Posted November 16, 2009 - 08:23 AM

#3

I had a YZ426 for eight years that did not require any valve adjustments whatsoever, although I checked several times. It needed no maintenance or repairs during my time of ownership, and was still strong when I sold it, with no clicks, clatters, smoke, or drips at all, and was still a one-kick starter.
It probably wouldn't hurt to replace the timing chain, as stock Yamaha chains are inexpensive.

  • davcon

Posted November 16, 2009 - 05:40 PM

#4

The timing chain absolutely.

How much total valve adjustment has been done? Two adjustments in 100 hours seems a bit excessive.


Good catch Gray! Verifying my records, the left and middle intake required one increment at 4.5 hrs. I checked them again at 32 hrs, no adustment required. Any thoughts on a new piston and rings?

  • grayracer513

Posted November 16, 2009 - 06:17 PM

#5

Piston and rings won't hurt anything except your wallet, and you might actually prevent a problem down the road by doing it. On the other hand, my '03 had well over 3 times that on it when it was sold. You just never know. If you're inclined, open it up and have a look.

  • davcon

Posted November 16, 2009 - 07:25 PM

#6

my '03 had well over 3 times that on it when it was sold.


Good enough for me, thanks!

  • Family Man

Posted November 16, 2009 - 09:46 PM

#7

Yeah but... your piston may or may not make it for hundreds of hours. You could be putting your motor at risk. If your just putting around it may last, or not. A new piston, cam chain and gaskets can cost under 200, if you do it youself.

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  • grayracer513

Posted November 16, 2009 - 10:14 PM

#8

That's why I said you never know, and it can't hurt.

  • roylo

Posted November 18, 2009 - 08:12 AM

#9

The timing chain absolutely.

How much total valve adjustment has been done? Two adjustments in 100 hours seems a bit excessive.


Im guessing the timing chain has a good chance of breaking after 100 hours, or does it stretch excessively or something?

  • grayracer513

Posted November 18, 2009 - 09:33 AM

#10

I don't recall ever seeing one break, but they can do one of two things:

They can start binding up, which causes "kinks" to form on the slack side. This can prevent the chain tensioner from tightening it because there may not be sufficient spring force to press the kinks out. That in turn can cause the chain to suddenly skip one or more teeth at low speed, or when starting or stalling.

The chain will, like any other chain, increase its pitch as it wears (called "stretching", although there is very very little true plastic stretch involved), and that increases the risk of skipping time and seriously damaging the engine, and it accelerates wear on the sprockets, especially on the crank. The bad part of that last, of course, is that the crank sprocket is cut directly on the left crank axle, and can't be replaced independently of that half of the crank.

  • roylo

Posted November 18, 2009 - 09:40 AM

#11

Looks like I better replace my chain aswell, thanks for the information.

  • roylo

Posted February 07, 2010 - 03:13 AM

#12

Is it worth changing just the rings and not the piston after 100 Hrs? I have 2 sets of them in the spares kit.

  • danZ73

Posted February 07, 2010 - 05:37 AM

#13

my manual says to replace the cams and cam chain together. it makes sense doing chain and sprockets but is this true with the cams too?

Edited by danZ73, February 07, 2010 - 05:48 AM.
misspelling


  • grayracer513

Posted February 07, 2010 - 09:29 AM

#14

The sprockets are only replaceable by replacing the cams. I have never replaced them as a matter of course along with a chain, only if the cam or sprocket was actually in need of it.





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