rebuilding clutch and engine on 2000 YZ426, need help

3 replies to this topic
  • Jorday

Posted May 13, 2005 - 09:24 AM


OK, the clutch basket blew up in this bike and ripped itself apart. I'm doing this work for a buddy of mine. Everything on the clutch itself looks ok, except the basket is trashed. What would be a good and relatively inexpensive way to get this replaced. The dealer wants 150 bucks for it.

For a long time when this bike used to run the clutch was really on/off, it never wanted to slip any so it was hard to get going without stalling. I've read of others having this problem with this particular bike, what is the cause and fix for this? Do I need to put a different clutch in it too?

Also, What is the deal with the 450 exhaust cam? Why don't you need to use the decompression with it? Are there any additional parts needed other than the exhaust cam out of like 03 YZ450? Lifters or anything? How much does it cost?

Is there a big bore kit available for this motor, like a 444 or something? How much does it cost and where is it available from? Is it as simple as having it bored and re coated and then putting it back together with a new piston, or are there other changes?

Any other mods worth doing or considering while it's apart?

  • Guest_BrandonV_*

Posted May 13, 2005 - 10:43 AM


I'm kinda in the same boat....
I recently seized my 2000 426 and have been replacing/upgrading as I go. I sent the cylinder to Luke's Racing in PA for the boring & re-nikasil'ing (they shop it out to Millenium in Wis), they did a 2mm bore (which is 444cc's) and are sending it back to me with a Wiseco 12.5:1 piston and gasket set for $350 even.
The 2000 clutch sucks! Search the YZ forum for the 2001 update info as they fixed the clutch in 01' and you can upgrade to those parts for about $100. I also bought a Perfomance Engineering clutch basket for $139 from Motosports Outlet, there's no reason to buy stock when a better, cheaper alternative is available. My stock basket was fine but I didnt want to take a chance when I can get a billet unit for $140.

To do the 450 cam mod all you need is a 450 exhaust cam, I got the 2003 model. Should replace the cam chain as well and check the teeth on the crank cam chain gear.

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  • grayracer513

Posted May 13, 2005 - 09:17 PM


The '01 clutch fix is what you need to fix problem one. Read this:

For the big bore kit, check out Luke's Racing

As Brandon said, the '03 450 decomp cam does the whole thing by itself, costs about $130-140. The cam has a shaft in the center of it that, when rotated, moves a small, ball ended pin in or out. The shaft rotation is controlled by a flyweight and a spring so that the pin is out at low speeds. At cranking speeds, the pin bears against the left exhaust valve lifter as the engine begins the compression stroke, and holds it off its seat until about 30-40 degrees before TDC, when it rolls of the lifter and the valve seats. This releases the first 2/3 or so of the compression stroke, but allows enough compression to develop so that the engine can start. Once running, the flyweight rotates the decomp shaft and retracts the pin. Very clever. It requires no adjustment or any real maintenance, and is totally self contained. The starting drill goes away ( the rules about when to use the hot start, choke, throttle, etc, still apply) and you can do a no brainer bump start like it was a 125.

  • Fastest1

Posted May 13, 2005 - 10:36 PM


Everything GR said, but you will need shims for the valves. Price of the cam should be 100.00 or less delivered.

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