2003 WR450 stutter???

Just picked up a 2003 WR450 with the free mods done. The bike seems to hit a rev limiter or the same feel every once in a while when coming through 2nd and 3rd gear.

What set up are you guys running in the carb?

I am at 1500' with a silent insert put back into the gutted exhaust and still using the stock spark arrestor screen. The bike will start with no choke and doesn't feel like it needs much warm up time. If I try to hold a steady RPM in nuetral the bike does sputter a bit. Wack the throttle and it hits hard and fast.

Any clue's?

You need to read the stickies at the top of the forum. You are covering several possible issues. The most common is the known defect (?) of the stock ignition coil that a large number of riders (not all) experience as a partial throttle 'stutter'.

Read the stickies and FAQ.

i have an 04'wr450 i just rebuilt the engine top and bottom end it has a stutter or missfire at 1/4 to 1/2 throttle to the point it is almost impossible to ride ordered a jd jet kit (not here yet) i have read all the posts i can find on this issue anybody had coil issues ,i have an 02' yz 426 and i know it has a slight stutter at steady cruise but nothing like this wr this one has me stumped

i have an 04'wr450 i just rebuilt the engine top and bottom end it has a stutter or missfire at 1/4 to 1/2 throttle to the point it is almost impossible to ride ordered a jd jet kit (not here yet) i have read all the posts i can find on this issue anybody had coil issues ,i have an 02' yz 426 and i know it has a slight stutter at steady cruise but nothing like this wr this one has me stumped

FROM THE FAQ STICKIE:

Q: Why does my WR seem to miss when I hold the throttle steady in the 1/4 to 1/2 turn range?

A: That's your TPS (Throttle Position Sensor

) doing it's job. Dirt bikes don't normally run with a steady throttle off road and they weren't designed too. Unplug it and see if the "miss" goes away. If so, then you know. You can also follow the procedure for checking the TPS voltage in the manual. It's extremely simple if you have a multimeter and some folks have found that it is set funky from the factory. Once properly adjusted, the problem goes away.

Well, not always. You can unplug it too.

Ya same problem I had until I unplugged that thing. I adjusted the TPS to spec and I couldnt get it there so I figured mine was bad so I was real close to ordering one but the price that Yamaha wanted was too much for me so I decided to just unplug it and now she runs much better! :thumbsup:

Derek

i unplugged the tps and rode the bike problem still there does that tell me that i am experiencing somethinng else coil maybe ? or cdi ?

wait for your jet kit to arrive. I know I had an extremely lean needle in my carb from the start so that may be your issue. What jetting are you running now? I have a 170 main jet, 45 pilot jet, stock starter jet (I dont remember which number it is) and a 42 leak jet.

as far as i know it is stock jetting the only thing i changed on the carb is fuel screw i added a white bros unit i am trying to get thing straitened out before 8-20 i leave for four days at hatfield and mcccoy i guess it might be some late nites i might just throw a new coil on it to be safe what is really frustrating is i went the extra step on everything in the engine and now dealing wiyh this issue i am a truck mechanic at a ford dealer and if i suspect somehting i can usualy see it some how i dont know how to see what i am looking for i am trying to come up with some testing out of out dated equipment laying around the shop i will wait for the kit

2006 WR450, 168 main, 48 pilot, GYTR kit needle at 2nd from top, zip ty fuel screw usually around 1.75 turns, stock everything else but Ti Q pipe, 4000' where i live ,and this bike runs FANTASTIC

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