WR 450 surges at constant speed

Great bike... one problem: When at constant speed (i.e. dirt road) and about 1/3 throttle, the bike has a miss and it surges. If I roll the throttle, it's ok. Anyone fix this problem yet?

Oh, BTW, After hauling the bike on my trailer a couple of times, I seem to have dumped the oil out of my left fork leg (I assume it is a blown seal). I have never really done any work on forks before. Should I tackle this job on my own or should I take it to the shop? If I should do it, are there any special tools I should get?



Before you redo the seals try this trick first. Get an old film negative and slide it up the tube into the seal. work your way around and see if you get any sand or dirt coming out. This is a common problem. A buisness card will work in a pinch also. As far as your hiccup, what mods, if any, have you done?. Read the posts on mods and especially read up on the jetting. Also, read up on the fuel mixture screw. I made all the mods, and it came down to the fuel mixture screw being off. Buy yourself a zip-ty replacement screw, and start fiddilin with it!


"Live well...ride free" :)

I have done the free mods minus the grey wire (I'll do it next time I take the tank off). I put in the 96db muffler insert. I have a 155MJ and a 48 PJ. Other than that it is stock.

OK, I don't want to sound too dumb, but... if I am getting sand out of my seal... what do I do?? Tear it down and clean it?? Replace the seals? :)


Mine is doing the exact same thing. On my last ride it seemed to get worse the higher the altitude was. I think it is happining on the transition from the pilot jet to the needle. I am running the GYR insert. I pulled to insert and it ran better so I think it is running to rich. I am going to drop the Nedle one position and see how it works. I will let you know how it turns out but won't have time to do it for a week or two.


The negative will clean the sand out. It works! You shouldn't have to replace the seals if this works.

It works!


"Live well...ride free :)


I'll just respond to the surging. Put in the stock YZ needle, 4th position. I could never get the stock WR needle to work right.


I understand from Vortex Ignition that the surge at constant speed is inherant in all 03 WR and YZ 450's. They told me that the problem lies in the stock CDI. I have the same problem with my 03 WR-450. Yamaha supposedly knows about this and should go back and fix them. Vortex told me that it is the way the power curves are mapped. I will buy a vortex ignition for the WR 450 when they are available. It nearly drove me insane while I was jetting my bike. Finnaly I thew the jetting thing out the window because the plug looked very good. You can re-jet the bike a hundred times chasing this mid throttle skipping I wore out my carb clamps!!!! Good luck!!!

RNS :)

Just about everyone I know who has a WR/YZF experiences the miss/surge at about 1/3 throttle and constant speed. On my bike it's around 50 mph in top gear. Leaning the needle helps with this but it never seems to completely go away. You'll just have to learn to love it. :)

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