My new YZ426F!!

I'm happy to say that after being away from the sport for 10+ years I've purchaced a 2000 YZ426F. The deal kind of fell into my lap so I couldn't refuse. It needs a little TLC but no major work. I had the local Yamaha shop check the valves etc... Everything seems to be in order. My plan is to get it into a trail freindly manor. I will be riding typical western conditions with a mix of tight single track to wide open forest service roads. Here is what I'm thinking:

Gearing it down a touch from the stock gearing

Replacing some damaged plastic

Do the 2001 clutch mod

Lighter oil in the fork

sofening up the rear end

Add a light (possibly to dual sport down the road)

New cockpit (bars,clutch lever/perch, grips, protectors)

I'm 6'0 215lbs. Any advice on modifications would be greatly appriciated.

By the way, this forum is unbalivable. The information is endless.


Lighter oil in the fork will do nothing for you. Modern forks operate on pressure differentials, and are designed to perform consistently over a wide range of oil temperatures. Normal shifts in oil temperature within the fork will change the viscosity of the oil far more than a move from, say, 7wt to 2.5wt will.

What does have a significant effect on the single chamber KYB fork that the 426 is equipped with is the oil level. The specified oil level is from 80-150mm from the top of the compressed fork (damper compressed, spring removed). Adjustment up or down within this range make a remarkable difference in the plushness of the stock fork, with the lower oil levels being much softer than the higher. If you are not doing a lot of MX style jumping or very high speed riding over rough ground, try it at the lower limit first. If the oil level is too low, you may notice an excessive amount of bottoming when, for instance you slam the bottom of a trail that runs down into and then back up out of a stream cut, or whatever jumping you actually do. You may also notice the fork damping seems to fade, becoming less controlled the longer you ride fast over ragged surfaces. In that case, the fluid is foaming, and the cure is to add a bit more. The fork will be very harsh with oil levels higher than 100mm down.

When you say you want to soften the rear, remember that you can only do that with the damping adjustment, and by changing the spring. Turning the spring adjuster changes only the ride height, and won't change the spring's stiffness. At 210 pounds, the spring is already a bit softer than it should be for your weight, so it may work out for you as is.

TRAIL friendly you would like to have less stalls and less abrupt power at the snap put a bigger flywheel on it. maybe a 13 oz? if i remember right. it tames the 426 down quite a bit for trail riding.

Congrats man! I had an '02 426. Loved that bike. Your gonna have a blast. I went to a 52 tooth on the rear and loved the difference it made for tight trails. A heavier FW is a must have also.

thanks guys. Since my purchase I have put 20hrs on the bike and made a few mods. The first thing I did was do the clutch lever mod and the acctuator arm mod, it helped a ton. I put a set of bar risers on it, gripper seat, new cockpit, new plastic, fork service and a bunch of cleaning. I am running 13/51 gearing in the bike and I'm really happy with it's trail manors. I may add some flywheel in the future but I actualy like the snap to the motor when you want it!! I am toying with the idea of a Recluse auto clutch. I'm just not sure I want to dump a bunch of money an older bike...

Adding flywheel weight will not reduce the snap of the engine to the point where it's gone. It will only take the edge off and add control and smoothness to the operation. You will notice NO power loss.

The Rekluse can be transferred to a 450 at a later time, or removed and replaced with stock parts and sold as used parts, if you choose. It's not like a paint job or something that has to stay with the bike.

Thanks grey. I didn't know if they were compatible with the newer 450's. I will probably end up on a newer 450 wr in the future so this is helpful information.

Hey Grey, does the WR require the same maintinence as the race bikes? They have a WR all super moto'ed out at a local dealer, been thinking about grabbing for some street fun. But I dont feel like changing oil on that every three rides like I do my yz

I have a 426 and even tho I'd love a new 450 for my cash situation the 426 is an incredible bike. I've loved it.

I would highly recommend the flywheel mod and the rekluse clutch. I have a hard time on tight trails some times and the combo I just mentioned would solve that problem all together.

Enjoy the beast.


Hey Grey, does the WR require the same maintinence as the race bikes? They have a WR all super moto'ed out at a local dealer, been thinking about grabbing for some street fun. But I dont feel like changing oil on that every three rides like I do my yz
If you use an oil that will hold up in the transmission for any length of time, you should be able to run the oil for up to 1000 street miles, depending on how you ride.

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