03 250f went back to dealer f/1/4 th miss

Took my kids 03 250f back to the dealer this A.M. for the 1/4 throttle miss. They confirmed that yes indeed there is a problem with the 03's. said I would have it back by this weekend to ride, not necessarily fixed but to race. Also they said one way or another the problem would be resolved.

Shop Mgr was fully aware of the Thumpertalk site and the 1/4 throttle complaint. I'll keep ya all up to speed as things progress.

I dont' know what you guys are talken aobut I don't have this problem.

Bigdrtrdr... Do yo have a YZ or WR? Everyone is freking out about this quirk, but my bike (01WR250F) had this problem too. However, With help from TT and a buddy who has the same bike, I was able to resolve this problem. Cutting the grey wire was a good start, tho it made me awful nervous!!! Installing a p-38 lightning was a HUGE help. The MISS, seems to me to be an overly rich squirt of fuel from the accelerator pump, which takes the motor a moment or two to get through. By leaning the squirt volume(P-38), the bike now has a nearly seamles acceleration curve, most good for low rpm snap wheelies :). I also removed the airbox lid, which further leaned out the fuel mixture. Upon doing this mod, it was necessary to rejet, and I wound up with these settings for humid 90-100deg. days: Main jet 178, Slo jet: 42, Air screw:1 3/4 turns from seated....

The bike now rips :D. It took some time, patience, and more time, but now the machine runs most excellentIMHO.

Good luck, but perseverance and the basic understanding of operating principles of a four stroke motor will lead you to the same result, methinks.

The WR's are different than the YZ's. The YZF problem is in the ignition. Hopefully Yamaha has a fix soon.


BK its a YZ and it aint no jetting problem. Ive owned 4 strokes for years, KTMs Kawi's suzuks...

This bike at about 1/4 throttle crusing along you would swear your riding a 2 stroke. It doesnt pop or sputter (lean Or Fat) it just flat missfires. Like a 2 stroke doing the 6 stroke.



My 03 runs perfectly, except at almost zero throttle in the pits, it surges. This is not a problem on the track, but it's anoying when I'm puttin'. Any ideas?

PS-Where's SPELLCHECKER on the Post Menu?

Old shark, sonds lean down low.

Dealers service called this afternoon and said they forwarded the ignition specs. from my 03 YZ250f to Yamaha. This dealer wants to resolve this issue.

I'll keep ya posted


bigdrtrider, you working wide Ride Motorsports on this on or someone else?

Lynnwood Motoplex, I have been buying bikes and parts from them for 20 years or more. Always taken good care of me. Plus they have a great new race program.



I like Lynwood Motoplex. I have never bought a bike from them..but they sure treat me good when I am in there. Did you know Ride now carries both Yamaha and Honda? Ride has alway done me well too.

Havent ever been to Ride but Ive heard good things about them. I tend to stick with one dealer, Loyalty seems to pay off. I'm picking up the 250f tommorow morning Fixed or not, the kid needs his saddle time. I'll take it back in when they have a cure. We will more than likely ride out in the power lines this weekend if you want to join us?



I'm sending off the paperwork to transfer the money to the dealer now. Trying hard to pick the new toy on Saturday! You guys riding Sat or Sun? Which powerlines? The ones out in North Monroe, or out at Reider, or other?

Most likley sunday, We can ride right from my driveway and hit some single track and powerline roads. It would be a perfect place to break in the new beast. You will need Saterday pm to tear it down and grease it properly anyway.

I live up in north Lk Stevens by Frontier Air Park. The power lines run between 84th "Getchel Rd" and Arlington.

There is about a 1.5-2 mile circuit to ride about 5 miles out. Sound Fun?

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