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caffd01

WR400 Exhaust on YZ400

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I recently bought '99 YZ400 with an FMF exhaust on it. Problem is it is way too loud for the woods. Has anyone fitted a WR exhaust(not header) on a YZ? I spoke to a cycle shop and the sales guy had his doubts about the bike running correctly. He mentioned the WR's different timing and cam, along with the fact that the WR exhaust is more restrictive and may hurt the YZ engine. Since I'm a thumper newbie, I need all the help I can get. Would it have any negative inpacts on the YZ engine? Would I need to re-jet? If so, what size? Let me know what you all think. Thanks guys.

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It may not clear the YZ side panel adequately, and the mounting hardware is a little different.

The YZ and WR have the same camshafts, but different exhaust cam timing.

A restrictive exhaust won’t “hurt” the motor, but it will require leaner jetting. A WR can “uncorked” is probably louder than my FMF Q silencer, and not much quieter than a stock YZ can. A “corked” WR can is extremely restricted, you can barely fit your pinky in there. If you have access to an inexpensive used WR silencer it may be worth a try, but I don’t think it will fit behind a YZ side panel. A little jetting adjustment would be the only other requirement.

Have you tried the stock YZ silencer? Much quieter than an ordinary FMF silencer.

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I picked up a used silencer on eBay and it mounted right on my YZ. No problems with clearance with the side cover. The problem I'm having is now I can't get the bike started. Would the more restrictive WR exhaust make starting more difficult?

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funny thing. We just did that this past sunday. It started 2nd kick. It had clearance. We used the same mounting hardware and rubber spacers. Ran great. Didn't miss at all. He said it Toned it down a touch but i couldnt tell still pulled the fronttire up through 3 gears. This was down the street. We are going to test it out this weekend to see how it does trail riding. Will keep you all posted. Baffel removed of course

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funny thing. We just did that this past sunday. It started 2nd kick. It had clearance. We used the same mounting hardware and rubber spacers. Ran great. Didn't miss at all. He said it Toned it down a touch but i couldnt tell still pulled the fronttire up through 3 gears. This was down the street. We are going to test it out this weekend to see how it does trail riding. Will keep you all posted. Baffel removed of course. much quieter that the yz pipe. Much quieter.

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How do I remove the baffle? Is it just a matter of removing the endcap and then what? Thanks.

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Originally posted by caffd01:

How do I remove the baffle? Is it just a matter of removing the endcap and then what? Thanks.

there should be a bolt on the wr pipe on the end. Undo and the baffel will slide right out. I have a 98 wr so it may be different for a 426. I dont know for sure.

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Originally posted by caffd01:

How do I remove the baffle? Is it just a matter of removing the endcap and then what? Thanks.

Also do you still have the fmf pipe and what kind is it. Would you be willing to sell it for cheap??

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The WR400 exhasut that I have has 3 bolts that hold the end of the can on. If you remove the end cap, there is packing around a metal "tube" (tube is really just 3 metal strips that holds packing) that is attached to the end-cap. Inside of the exhaust there is a metal disc with an offset hole about 1.25" in diameter welded in place. I don't want to cut the "tube" away from the endcap because then I wouldn't be able to wrap the packing around anything.

I think I will keep the FMF for track riding.

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Originally posted by caffd01:

The WR400 exhasut that I have has 3 bolts that hold the end of the can on. If you remove the end cap, there is packing around a metal "tube" (tube is really just 3 metal strips that holds packing) that is attached to the end-cap. Inside of the exhaust there is a metal disc with an offset hole about 1.25" in diameter welded in place. I don't want to cut the "tube" away from the endcap because then I wouldn't be able to wrap the packing around anything.

I think I will keep the FMF for track riding.

well on my wr stock pipe there is the three bolts also. But on the smaller pipe that the last air runs through there is one bolt that holds the baffel in. I didn't have to undo any of the three bolts that screw in towards the engine. The bolt i took out was screwed in towards the heavens. Maybe yours dosent have one. I dont know with out seeing it.

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Ok, stupid me. I looked at the end cap and the baffle was already removed before I bought the WR exhaust. That explains it. Well, I'm going to give it a shot and see how it works. Thanks for your time.

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