02 yz 426 valves


5 replies to this topic
  • andyroo

Posted September 12, 2008 - 02:26 AM

#1

Can some body give me direction with my issue. I have to replace all valves but i know Steel is the better option which is what i am going to change too. But my problem is. Will OEM 2000 426 valves and sprigns fit a 2002 head with out any issues. Has any body done this. I dont rev the engine hard so changing from titianum to steel wont give me any problem. Any info would be appreciated.

  • matt4x4

Posted September 12, 2008 - 04:50 AM

#2

you can get aftermarket SS valves and springs specifically for your year make/model of bike.
Since Kibblewhite valves are identical in part number for 98 to 2002 yz/wr400 and yz/wr426, I can confidently say that installing 98 or newer SS valves will work fine - just make sure you redo guides, seals and seats.

  • grayracer513

Posted September 12, 2008 - 05:01 AM

#3

Steel is not better. Then again, in a YZ426, it's not really worse, either. It is different. The weight can be a problem, but Yamaha never had any trouble controlling valve float, so that doesn't matter so much. They don't really last any longer than Ti valves, either, but they also don't have the sudden accelerated wear at the end of their wear life that Ti does. But, they are a hell of a lot less expensive, which makes them a rather practical choice.

And yes, the '00 valves and springs will drop right in. BE SURE you use the '00 springs.

There's no reason at all to bother with Kibblewhites on a 426.

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  • matt4x4

Posted September 12, 2008 - 05:36 AM

#4

but they also don't have the sudden accelerated wear at the end of their wear life that Ti does.


I think this is key for those less apt to check their valves REGULARLY - all of a sudden, it makes lots of sense to go SS - Out of 20 people I regularly ride with, 18 would be better off with SS valves and only 2 would catch Ti Valve wear before it gets to critical/destructive.


I wasn't saying to get KW valves, I find it's just easier to look up an aftermarket part# for multiple years then looking up numerous microfiches for numerous years when aftermarket covers a multitude of years in one number.

  • grayracer513

Posted September 12, 2008 - 06:15 AM

#5

I think this is key for those less apt to check their valves REGULARLY - all of a sudden, it makes lots of sense to go SS - Out of 20 people I regularly ride with, 18 would be better off with SS valves and only 2 would catch Ti Valve wear before it gets to critical/destructive.

In most cases, if one was to have a Ti valve wear through its coating before the wear was caught in a clearance check, the first real symptom would be a loss of compression when cold, coupled with extreme difficulty in cold starting, even to the point that the bike can only be push started. The people who get into real trouble are those who ignore this, or who reshim, perhaps multiple times, to a size .10mm or more smaller than the original shim. That's when there is a very real risk of breaking a valve stem and basically destroying the engine.

And I understood you on the KW's. I just wanted to make the point clearer to anyone who may not have.

  • andyroo

Posted September 12, 2008 - 03:53 PM

#6

Thanks for your responces. Answered my question. The issue i had was just after buying it second hand it was getting hard to start and popping through the exhaust on decell. The first thing i did was replace the plug which helped a little but not enough, so i pulled the rocker cover and found zero clearance on the middle intake valve. The smallest shim still would not get it to stop riding. After pulling the head i found all intake valves worn. I was tossing up to go with SS Valves but after reading other threads on TT i went looking for 00 valves which are alot cheaper and for what i do any power loss isn't an issue. Once again thanks for your help.





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