YZ426 Advice

I recently picked up a 2001 yz426 in june and have put about 20 hours on it since. I have been great about maintenance on it since I bought it and decided to check the valves for the 1st time.

I1 .068

I2 .102

I3 .102

E1 .178

E2 .178

What would you recommend I do. Reshim them or replace the valves over the winter. I have no clue about how many owners on the bike of previous doings. It rode solid and I love it.

Reshim I1 and check it every 3-4 hours for the next 16-20 or so, If it needs replacement, it will not hold the clearance you set it to for longer than a few hours. If it's still good, it will stay as you set it.

Should it be okay for the occasional ride until I store it for the winter? Maybe 5-10 hrs at max before i address the issue, or is this something I should be doing now before starting it again.

At the very least, check it after the next ride to see if that valve has closed up more.

Understand the problem: That engine has Titanium valves. Normally, from the time they are first assembled, they will go for years without needing a valve adjustment. Then, eventually, the thin coating of titanium nitride that makes them hard wears through, and they start wearing very quickly. Once any one valve has gone to the point where the shim it needs to be at the proper clearance is more than .10mm smaller the what was there to start with, or will no longer hold the same clearance setting for 5 hours or longer, it's time to replace the valves.

Letting them go introduces the risk of dropping a valve head due to stem flexing caused by a worn valve face scrubbing sideways on the seat as it closes.

426 owners do have the option of using the stainless steel valves and matching springs from a 2000 model. These are less expensive and even more durable than the OEM ti valves are.

426 owners do have the option of using the stainless steel valves and matching springs from a 2000 model. These are less expensive and even more durable than the OEM ti valves are.

I've seen on the kibblewhite web site that they make white diamond stainless steel valves for the 426. Is it just a missprint? Anybody ever switch to these? I was thinking of switching to them. Much cheaper and more longevity. http://www.blackdiamondvalves.com/default.htm

The KW valves are significantly less, but because stainless steel is nera twice the weight of titanium, the springs must also be changed, and the KW spring kit is something like $250 dollars. Feedback kI've seen from Honda people who went to these to cure their early CRF ills is that they're not that much better than stock CRF Ti stuff in terms of reliability.

If you had a YZ450, there might be a valid debate about it, but not on a cost basis, as the savings would only be on the order of 7-15% overall, and the durability of the OEM Yamaha Ti valves is above reproach.

However, since we're talking about a 426, you could use Yamaha's OEM stainless valves and matching springs from a 2000 model for less than a quarter of the cost of OEM Ti stuff, and these may be the only thing more rugged than the OEM Ti.

Should it be okay for the occasional ride until I store it for the winter? Maybe 5-10 hrs at max before i address the issue, or is this something I should be doing now before starting it again.

Personally, I'd reshim it. It only takes about an hour. I'd go ahead and reshim the exhaust valves too.

I'd go ahead and reshim the exhaust valves too.
Good point. That didn't click in right away because they're both the same and that figure is perfect for a 250F. My bad.
Good point. That didn't click in right away because they're both the same and that figure is perfect for a 250F. My bad.

I was kind of shocked that you didn't catch that......

My mind is fresh from a weeks long vacation in Jamaica. I doubt anybody missed me, but I'm back. :thumbsup:

However, since we're talking about a 426, you could use Yamaha's OEM stainless valves and matching springs from a 2000 model for less than a quarter of the cost of OEM Ti stuff, and these may be the only thing more rugged than the OEM Ti.

You are sure that the 2000 model will work in a 2002? Thats a 400 right?

You are sure that the 2000 model will work in a 2002? Thats a 400 right?

The 2000 YZF was a 426. 98/99's where 400's.

The 2000 YZF was a 426. 98/99's where 400's.

Yeah, my bad. The wr was still a 400, I was thinking they both were. Thanks though.

The 2000 WR was a 400, but the 2000 YZ was a 426, and yes, they fit the 01/02.

You are sure that the 2000 model will work in a 2002? Thats a 400 right?[/QU

NO THE 00 MODEL YZ426 IS WHAT HE IS REFERENCING I DO BELIEVE....BUT THE WAS A WR MADE THAT WAS A 400 IN 00, THE LAST OF THEM....IF I NOT MISTAKEN THE 00 WHICH IS WHAT I HAVE...CAME WITH STAINLESS VAVLES...I THINK THEY SWITCHED IN 01

BUT THE PARTS ARE CHEAP FROM THE TT STORE IF HE WAS TALKING ABOUT THE 00 426

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