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Dougie

Anyone with a 400 do a top end yet?

6 posts in this topic

I'm giving my '99 WR400 (YZ'd) a good once over this year. New plastic, light, handgaurds, Big Gun exhaust system, etc. I'm going to do the valves and I am wondering if I should do a top end also. To do the valves, I will not take the engine out, but if it needs a top end, I might as well take it all the way out. (I will do my own valves, but take it in for a top end).

I know 4 strokes don't need them hardly as much as a two, but it has been 5 years now. Has anyone needed to do this yet on their 400?

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I have done my 98 yzf 400 it wasn't that hard to do. I did the top and bottom end. Just went by the manual and if I had any questions I had a friend I could call. The top end is super easy.

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Once the head is off, its not much work to get at the top end. Its certainly worth having a look. I was at a tech session where we took one apart and measured everthing up. The valves needed to be done, the cylinder was perfect and the piston would have been perfect, except it was worn at the wrist pin. The bike had about 20000 km on it (1999 WR400)!

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Doug, if it was me and I had the head off, I'd slide the cylinder off, replace the piston and rings (up the compression if you want at this time, they have a 13.5:1) and at that time, check for any side play in the crank bearings and rod bearings. Are you doing your own valves? If so, the best setup for a DIY on the planet it "Neway" quick cutters for the seats. We use these at our dealership and its so slick, but spendy. You can buy only the pieces to do just the WR400/426/450. Grinding the valves will require a machine or the Neway valve grinder. If you needed just the valves ground, I could do them at work, PM me if you need. Some valves are small and the "margin" is thin to where they may not have enough meat to clean up and still have enough "margin" left, but you dont know till you try it. ;D

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i also have a 99 400, when we talk about 'doing the valves' are we replacing with new ones or ...?

thanks :cry:

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While your there DO the YZ 450 Exhaust cam Mod, it was the best bang

for the buck I have ever done to a bike, and I have dropped some

big money into em.

I was going to sell my 01 WR 426 and after the cam mod I will definitely

keep it, starts first kick and no decompression lever to mess with not

to mention the low and mid range curve that it really smoothed out

with no loss on top:thumbsup:

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