03 wr 450 missing

I have a 03 wr 450 with a bout 200 miles on it. Last summer it started missing, popping, stuttering past 1/3 throttle then cleared.I read about the woodruff key problem and had the dealer make the repair. The first owner had the following mods made prior to the bike leaving the dealer. Big Gun exhaust with header and air box mods. This year, I cut the grey wire, placed additional mods to the air box cover and installed a JD stage1 jet kit as directed.

Well guess what? The problem is back. So, I completely dissassembled the carb and cleaned all the passages and even tried jetting changes. The result was a leaner or richer running machine with the same problem. I figure that since the problem begins past 1/3 throttle and does not go away, it has nothing to do with the carb. In my last effort tonight, I replaced the plug thinking it may be just that simple. We will see what happens tomorrow.

If any one has some ideas, thow them my way... Thanks!

If it is studdering it is rich. You say it is at 1/3 throttle, so drop the needle a clip (go leaner) and problem should go away.

Actually it is past 1/3 throttle and all the way through to wide open.

Thanks

start with the needle.

Check to make sure the carb is seated properly into the rubber boot on intake side of engine. Also check to ensure intake rubber is not cracked or split.

Ferg

We've also had to adjust the TPS to get it back into spec.

TPS was my problem too.

Thanks, Lowering the needle helped quite abit . I still have abit of a stumble. Ironically the boot on the intake side was not square and possibly sucking air. I will check the tps next. However it runs much better.

Thanks Folks

We've also had to adjust the TPS to get it back into spec.

What are the specs on the TPS?

Yamaha service manual states:

Adjust:

TPS output voltage

Adjustment steps:

Adjust the installation angle of the TPS 1

to obtain the specified output voltage.

NOTE:

Measure the output voltage accurately with a

digital electronic voltmeter that gives an easy

reading of a small voltage.

TPS output

voltage

Tester selector

position

0.58 ~ 0.78 V DCV

Hey, if it is an 03 and has that few miles on it. Maybe it sat long enough to gob up the petcock and you need to pull it out and clean it with some brake clean and small brush??!! Jason

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