Questions on a YZ426 Motor

first id like to say you guys have a great forum here, now for my questions. i just picked up a 2000 yz426 bike for a killer deal. thing looks new but needed the tranny gears replaced, i bought the whole bike from a dealer where the previous owner had left it because he couldn't pay the bill, i gave $310 for the whole bike. the motor is going in a 2000 honda 400ex quad frame. need to know what to look for as to problems that may arise with this motor. right now it is down having the gears replaced. while it is down we decided to do a few other things to it. bought a je 13.5 to 1 big bore piston which will bring it up to 444cc. also going to replace all the valves and seals while it is down since these parts are so cheap. we have also bought a hot cams exhaust cam with the auto decompression, now are there any weak points on this motor that we should address while it is tore down, if anyone is interested the rest of the bile will be parted out very soon and as i said it looks new and has a few aftermarket parts on it, it has a d & d exhaust system on it, are these any good, never heard of them in the quad racing world. thanks in advance for the input.


If you can afford to upgrade/update the crank to the 01 spec do it. The balancer shaft drive gear is driven by a square key on the 00 and before. The 01 has a splined gear drive. Other than that its a great engine.

A good clutch basket would be a good idea too. The steel insert that is cast into the OEM part sometimes shakes loose and allows the entire clutch pack to wallow around. It took me quite a while to figure that one out...

I think you may have a "Dr.D" exhaust system on it. I just picked up a 00' 426 also and it has stock exhaust. If you want to part with the system, give me some details and a price. I may want it.

thanks, i had heard that about the cranks on this year, rather than buying a whole crank couldnt i just buy that half and the splined gear. i was just looking at the parts diagram for both years, crank is about $350 and just the crank half is $132. just a thought.


I just had a 2000 426 burn a con rod bearing (big end). Be sure to change your oil often and use a high quality oil. The mechanic said it looked like no oil starvation occured. Just lots of miles. I was riding it about 25 miles a day for more than a month. So it took a bit of abuse. Do the 2001 clutch upgrade, as well. It will make engagement smoother.

thanks, i had heard that about the cranks on this year, rather than buying a whole crank couldnt i just buy that half and the splined gear. i was just looking at the parts diagram for both years, crank is about $350 and just the crank half is $132. just a thought.


Getting the crank together correctly (that is, perfectly straight) might be tricky. Unlike many two strokes you can't get a crank jig to set this up.

Unless I knew a skilled mechanic to reassemble the crank I wouldn't try it.

While the '00 crank w/ its keyed balancer drive gear can be an issue I think it can be perfectly reliable if you keep an eye on it, make sure the keyway in gear and shaft is undamaged, and use hardened key stock to make your own key (make sure it isn't overly long, this will interfere w/ torque value on main nut).

thanks for the info. as far as the crank a buddy works for a yamaha dealership and could do it for me. he is the one that got the bike for me and all the parts to fix the tranny. man the mark up on stock parts is a killer, his price is almost half what you or i would pay for them. probably run it like it is as we tear down often to inspect. this motor is going in a race quad only.. see if i can find a good pic to post of the quad it is going in. i know ya'll are bike guys but thought you might be interested in what the motor is going into.


this is what the motor is going in.


thats bad ass ,who does your graphics

Hey if you are parting out the bike I'm wondering what you're asking for the rear wheel and hub assembley?

the graphic kit is from k & k atv parts. not sure on the wheel and hub, dont know anything about bikes so i dont know what its worth. throw me an offer and we will go from there.


Hey, it wouldnt happen to have bark busters or radiator braces would it?

Hey Quaddad, I sent you a pm.

I wonder how cheep ya can build a race quad starting from a parts bike and the frame and all that from ebay??? I remember a few years back when I wanted to race mx on a quad I figured the cost being $16000 starting from a new quad and getting all the nessary parts. :) I like bikes better because they come race ready :)


I have bark busters off of mine if you want them!

I bought and parted out a 2002 yz426.

They are Moose racing and are white.

Free if you pay shipping.

I live in Texas.

Email will do pics.


got your pm, just havent had time to answer it, that quad has $17,000 in it but is just not competative anymore since the new 450's have come out. too much to build a totally new one so we are installing the modded 426 in the frame. the front and rear shocks alone are over $2000. yea quads are expensive to race but that is what my boys like. i will post a pick of my 11 year olds mini quad. started out as a 99 eton 90, now the motor has been bored and stroked to 110cc plus it has all aftermarket suspension liike the big one.



Just imagin what kind of bike youd have for 17 G's :)

My buddy races a modded 400ex w/$14,000. The new 450 quads are just to quick. Like you his chassis if fine just needs some yamie power :)

Double check the exhaust. It could be D&D or Dr. D. D&D is mostly street so I would be surprised if they had an exhaust for the 426, but it is entirely possible. Dr. D is more popular and quite a good exhaust so you should be able to get some money for it on ebay.

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