Suggestions on how to improve a stock canadian pipe for a 2002 wr 426

I've run my bike for a while in its stock form. And so far the blue machine fills every bit of my ability and much more. :D

But being a neolitic male :D , I'd like to open up the exhaust a little bit more to gain free hp and may be more throttle response. So far the jetting seems to be right on. It starts first / second kick and backfires lightly when really hot, like in slow mud plowing. Otherwise it runs great. :)

I know that the best way is to install an after market pipe, and there are many available out there :D. But I'm not ready :D to put out the $$$, and put up with the noise and all the jetting issues that a pipe brings.

I like simplicity :D

Even if I'm looking for a "cheap" solution, may be some of you have suggestions for an after market pipe that would improve the ride without too much troubles ?

But to begin, I'd like to know if there are any mods to be done to the stock canadian pipe for improvement ? Other than ripping it off the bike to trash it :D



Yamaha wr 426, 2002 Canadian edition, street legal, Uni-filter, Devol rad guard, Works frame savers, Acerbis hand guard, full skid plate, Trailtech Endurance bike computer, and more scratches...

Well, I dont have an answer to your question, but I have a question for you if you dont mind. I too, have a street legal 2001 WR 426, but its illegal equipment wise, I'd like to know what lighting kit you used to get it street legal, ie Baja Designs etc and do you have a picture of it?


I'm on my third Canadian WR426/ 450.

Buy a Supertrapp 4" standard insert replacement and the 6 or 12 disc set.

Cut off the end of the muffler on the engine side of the weld with a hack saw or sawzall (new blade). Saw slower because it's stainless. Cut the 4" insert shorter so it will fit inside the muffler. The insert is tapered and taps in perfectly, but only tap in part way so you can mark 3 holes for drilling. Take the insert out, drill the holes, tap back in and bolt on (bolts do not come with the insert. Total cost about $70USD and it's adjustable for power/ noise! It took me about an hour to do this as I was taking a saw to a bike that had never been started. Put duct tape next to the cut line so the stainless muffler does not get scratched when the saw blade deflects. I bought my supplies from


Sylvain, pm me your e-mail address and I will send pics of my stock pipe upgrade. It really improved throttle response and only upped the noise a little. WR Dave. :)

I have to be honest with you. The bike is street legal as long as I don't have to pass an inspection. OUPS!

When I bought the bike (new) I went to the licence bureau and told the clerk that I wanted to licensed the bike for the street. The bike has to be insured for the road and the plate is much more expensive for the street. I added the equipement and I try not to draw attention when I ride my bike. I don't intend to use the bike on the street too much. It's mainly to get to the trails nearby.

I made my own kit. I kept the original lighting equipement. So if I really want it to be "legal" I would have to install DOT approved lighting equipment. Just like you.

Sylvain, pm me your e-mail address and I will send pics of my stock pipe upgrade. It really improved throttle response and only upped the noise a little. WR Dave.

It's done



Does any of the SuperTrapp components have the spark arrester wording on them? I have two of these pipes & your idea sounds great.

You got my attention Colorado Tim, :)

I went to mxsouth to have a look at the parts. To tell you the truth I'm a bit confused about the parts.

Since you already made the set up, please could you give us the part# ?

There are a lot of options to choose from. It would really facilitate my quest.

Did you have to modify the jetting ?



The Supertrapp solution does have a spark arrestor and is stamped "USFS Approved Spark Arrestor". Pretty sweet.

Here are the part numbers for

#10-772 Pro Series Core Kit...$33.50 (slides into muffler)

#10-770 Diffuser Disc 4" 6 pack...15.09 (also comes in a 12 pack for more power/noise)

#10-423 Strpp stnls 6BOLT 17.25 (spark arrestor)


Tim, your Supertrapp solution sounds great. Looks like I will be trying it. MXSouth web site is a good one-it is now in my favorites. I have posted before about my Canadian WR450 having a 1/8 to 1/3 throttle hesitation problem. Have you had any problems with hesitation with or without your exhaust modification?

Thanks for the pictures :D

I made the mod to my pipe, 8 holes of 3/8" diam.. It certainly brought life to my bike. It's noiser but not to the point of being offensive to others. Of course I don't twist the throttle too much when I'm close to homes. I don't really feel that there is much more power overall but one thing I noticed is the engine revs faster and things happen faster too :D.

But as a drawbacks (I think):

There is more bacfiring when on decell from full throttle.

And I feel it may have lost some snap for 4/5th gear wheelies. :D

Which leads me to beleive that I may have to richen the mixture. :)

I'm not very comfortable about starting to play with the jetting. I'll get more info on that subject from Taffy's topics :D before I play with the carb's set up.

And I'm still looking for a USA YZ pipe for a reasonnable price. :D

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