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YZ400Court

need a yz/wr cylinder head

10 posts in this topic

I am looking for a 1998 to 2001 yz/wr 400/426 cylinder head. I broke a shim bucket and destroyed the head. Anyone knowing where I might find one used please let me know.

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Pretend it's flat and give it the gas.

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There's a company that had a huge ad in one of the mag's , that says they can repair any cylinder, and cost less than new !!!! I think it's USCHROME (920)-922-5066. I can't find the mag with the ad but as soon as i do i will confirm if it is USCHROME ! hope this helps ?

Canadian Thunder !

[This message has been edited by YZ426FJH (edited 04-11-2001).]

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Thanks for thr info. I got tired of thinking about rebuilding my 400 with 426 parts, and bought a complete 2001 yz426 engine (new in the box). I should have it ready to ride next weekend at the Kachina Enduro in Santa Fe.

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Pretend it's flat and give it the gas.

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Whoa! How much did that set you back? Will you be parting out any of your 400F motor parts?

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The new engine (still in the Yamaha crate) was $2500.00. A steal for a brand new 2001 YZ426 engine. I think I'll hang on to the old one for now, although only the crank, transmission and cases are salvageable.

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Pretend it's flat and give it the gas.

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When I priced parts to rebuild my 400 it was $1700.00. I don't get a warranty, but I do get the stronger crank/rod combo, and TI valve setup.

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Pretend it's flat and give it the gas.

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YZCourt: Might I ask what caused your shim bucket to break...chip..or whatever happened to it? Was it just one? An exhaust? Intake? What happened after it failed? Did it damage a valve? I'm very curious as to the cause of these types of failures.

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I could have used the crank.. My rod bearings blew appart when I starved my motor of oil from doing really really long wheelie's .. about 1/2 mile :)

The oil pick up in the bottom of the cases I have been told doesn't draw any oil when the bike is straight up..

Riders BEWARE of this.. 426's LOVE to be wheelied. Cost me 1400 canadian funds to buy the parts for that screw up.

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Boit,

I dropped an intake valve. The intake valve got wedged between the piston and the exhaust valves. The exhaust cam came around and tried to open the valves, but there was a valve stuck under them, and presto, both exhaust buckets shattered. The cam then drove the pieces of the buckets into the soft aluminum holes where the buckets should ride. It really tore up the machined surfaces where the buckets ride. I noticed Yamaha has .020 over shim buckets, so I thought I may be able to machine the holes and use them, but the bike akready had them from the factory. I had an e-mail conversation with BK of Yamaha, and came to the conclusion that overreving caused the valve failure. The rev-limiter does work, but several times during the race I had missed 2nd gear(I seem to have a very big neutral). It was 2 or 3 turns past my last missed shift when the valve broke. Unfortunatlly the top end of the rod was also destroyed.

Unfortunatlly this problem occured only about 20 hours after breaking the top end of the rod in the same motor. After a full season of desert racing, the bike was rebuilt with a weisco 13.5-1 compression 420 kit. Head ported, cams degreed, big gun pipe, and lots of dyno time. What a monster, tons of midrange torque. The next race was a lot of 100mph sand washes. In one of those washes the top end of the rod cracked straight down from the piston pin. the piston then bent some valves, and the race was over. I could never gat a straight awnser from anyone why the rod cracked like that, until I spoke with Stroker the other day. They said the rod was just weak. Barely strong enough for the stock 400. That is why the rod and crank have been redesigned for the 426. They reccomend changing the rod in the 400 every season. BK suggeted i use 2001 426 parts instead. He said the Titanium valves were a lot tougher, and would take the overrev abuse better, as well as the crank and rod being a lot better.

I had priced all 2001 426 parts, head, titanium valves, springs, piston, cylinder, crank...ect. It was around 1700, and I still had to find a place to put the hot start hose, as the 426 has it mounted on the carb, not the cylinder.

I think the new 426 engine is a better idea than rebuilding the old 400, although I still need to find a place for the hot start hose.

If it blows up again, I will burn it in the desert and buy a KTM 520 MXC. As a matter of fact I am going to buy a 520 in the fall anyway. :)

What fun!!!!

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Pretend it's flat and give it the gas.

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Ontario,

I wish I could ride a wheelie long enough to blow up my motor. I usually just end up on my butt after 30 yards or so :) Sorry to hear it cost you so much.

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Pretend it's flat and give it the gas.

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