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07 WRF suddenly stumbles-big ride comin up-please HELP!

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07 WR250F over night suddenly stumbles on top end(super fat sooty plug). I took it to the guy I bought it from(also has a shop) and started messing with the main jet. It now will rev through the range but not with good power! Its also starting to stumble a little over the whole rev range. Its not guttless just lost its punch. It starts faster than I can press the button, has very good compression. Im down to a 160 on the main jet and still sooting up the plug.

Mods= exhaust restrictor removed, snorkel removed and Boyseen Quick Shot 2. I have the biggest ride of this summer coming up next weekend. Please HELP! Im in central MN.

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Heres what I f'd up tonight. Went to change the needle clip setting just to realize it dosnt have settings. When I went to put it back together something happened. the throttle no longer pulls smooth. Something feels jammed in their and it wont even return right! I put the slider back together right with all the balls(?) in the same spots as it came out(at least I think so) Whatever got screwed up seems to be with the bracket the cable directly operates but not sure. Any ideas???

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Did you get the little plate on the carb slide back in correctly? You didn't turn it around and put the seal side to the carb body did you? Soundsl like you pulled the whole carb slide to pull the needle? Not needed. simply remove the cover, remove the allen screw on the top of the slide and wih a small set of needle nose pliers, remove the needle.

Keep this liitle idea in the back of your mind when jetting as it will help.

Fuel screw effects from idle to about 1/8 throttle the most

pilot jet is from idle to about 1/4 or so throttle

needle does mose of its work in the 1/4 to 3/4 range

main is 3/4 to WOT.

leak jet in carb effect how much fuel is returned to the carb bowl verses thru the accelarator pump nozzle (meaning it will effectively be just the opposite of the thinking of other jets, bigger makes the ap squirt less, smalle means more)

Make sure you have no air leaks and the air filter is clean and not over oiled when jetting.

That said, if you are getting a sooty plug, I assume you are swapping with a new plug and not just jetting, runnin the bike then checking the same plug?

Unless you know how to read a plug well, have a hand full of new ones and are the one riding the bike when you are reading plugs for jetting its going to be tough to you this method to jet. It is a good way to reference jetting, however unless you really have good experience and are diligent about how you test it, just running a plug to check jetting only gets you part of the way there. it is a look at over all getting at that point

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Ok, ive missed 2 rides, had the bike to 2 shops and still misses in the top end. Both shops gutted the carb and said it wasnt the carb. next week their going to look at elec. The carb is back to the jetting when it ran good. Its good in the low and mid. It sputters/misses in the top end of the rev especially under a load. Plugs still coming out black.

Come on guys, anything you can think of that could be elec related? Been a couple of weeks now.....

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you need to get a jd jet kit or some other needle that can be adjusted. put the original main back in, get a fuel screw, if you don't already have one, and put a 50 leak in and it will run good. thats what i did. the jd kit will also have the o ring mod for the ac pump. cut part of your tail pipe out, not just the "restricter", like what's in this thread http://www.thumpertalk.com/forum/showthread.php?t=470292&highlight=muffler+mod i posted pics. and for extra torque, put a 51 tooth on the rear.

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I have the same problem and same year bike

Yesterday during a long ride, for the first time in 200 miles the miss went away. I let the bike sit for 5 minutes, restarted and it came back.

I have put in a new sparkplug cap/coil and rejetted it to JD jetting specs.

Nothing has worked.

I think the CDI is totally suspect. Especially after talking to a local technician.

I am going to try to get a guy I know with the same bike to let me swap CDI's.

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I have the same problem and same year bike

Yesterday during a long ride, for the first time in 200 miles the miss went away. I let the bike sit for 5 minutes, restarted and it came back.

I have put in a new sparkplug cap/coil and rejetted it to JD jetting specs.

Nothing has worked.

I think the CDI is totally suspect. Especially after talking to a local technician.

I am going to try to get a guy I know with the same bike to let me swap CDI's.

Please, please post your resaults here or PM me. I know their not the same at all, but I had a sled that did the same thing and the CDI was the culprit. For the sake of a fix, I hope thats it. Does yours pretty much rip on the bottom and mid but not the top? Keep me posted, Im bringing mine back to a shop later this week, Be great to go with some info. Jason:worthy:

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160 sounds super lean, find a dyno shop to re jet your bike with a wideband.

if the plug is white its lean, but still sounds like your running rich. I would get a new needle and put it one setting higher, to drop the needle down 1, so the top end would be a bit leaner

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160 sounds super lean, find a dyno shop to re jet your bike with a wideband.

if the plug is white its lean, but still sounds like your running rich. I would get a new needle and put it one setting higher, to drop the needle down 1, so the top end would be a bit leaner

Its not the carb/jetting. This bike ran perfect then suddenly-shit literally overnight. We tried different carb settings and nothing even came close- still a black plug. Many people are now pointing to elec. Ill get it back to the shop later this week. I was just hoping to bring it back with some more info.:)

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Any updated news on the problem and or solution.....?

Bob

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Any updated news on the problem and or solution.....?

Bob

A tech tested everything. Nothing seems wrong. Ive got a new CDI coming this week. I will post with the resaults.

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A tech tested everything. Nothing seems wrong. Ive got a new CDI coming this week. I will post with the resaults.

:thumbsup: Well, F:censored: K, F:censored: K, F:censored: K. I go my new CDI in today, After $130 diagnostic to tell me it needed to be replaced, $197 for the CDI and 2-months of wait time. The resault is that it's unchanged. Still not fixed!!!!

Im out of ideas and dont know what to do anymore.......God, I may have to bring this thing to the dealership?!

Anybody need a new CDI for cheap? LOL!!!!!!!!!!!

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:thumbsup: Well, F:censored: K, F:censored: K, F:censored: K. I go my new CDI in today, After $130 diagnostic to tell me it needed to be replaced, $197 for the CDI and 2-months of wait time. The resault is that it's unchanged. Still not fixed!!!!

Im out of ideas and dont know what to do anymore.......God, I may have to bring this thing to the dealership?!

have you tested your coil? checked all your connections for erosion? check your grounds?

sounds like your not getting a spark half the time or something.

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have you tested your coil? checked all your connections for erosion? check your grounds?

sounds like your not getting a spark half the time or something.

Checked the coil and T.P.S, not the grounds. I wouldent even know where to start!?

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Did you check and confirm valve clearences and that the cam sprocket(s) did not move on the cam(s)?

No, could this affect topend only? The bike runs mint on bottom and mid. If I twist the throttle 1/2 to 2/3 and hold it, it will rev out smoothly. When I twist from this suddenly to W.O. thats when it stumbles.

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No, could this affect topend only? The bike runs mint on bottom and mid. If I twist the throttle 1/2 to 2/3 and hold it, it will rev out smoothly. When I twist from this suddenly to W.O. thats when it stumbles.

usually it affects idle, and to me didn't feel like it affected top end much, but that was a honda, I've yet to ride a yamaha with tight valves

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usually it affects idle, and to me didn't feel like it affected top end much, but that was a honda, I've yet to ride a yamaha with tight valves

Yes I agree, and with the many posts Ive read on Yam valves, when they get tight they are hard to start. This bike practically starts before the button is fully depressed. Also by the sounds of this motor, it seems the valves are not tight.

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You've been all through the intake tract, and it's not plugged (mouse nest, ping-pong ball inserted by riding buddy, KTM sucked into intake)?

Is your air filter completely munged up?

Is your carb slide lifting all the way?

Did your buddy jam a banana in the tail pipe?

Check the intake cam lobes, make sure they're OK.

Take the head off, and make sure that the intake valves are actually opening all the way.

Sounds like it's not getting enough air. This would act worse at higher throttle settings. Figure out why, and you might fix the prob.

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You've been all through the intake tract, and it's not plugged (mouse nest, ping-pong ball inserted by riding buddy, KTM sucked into intake)?

Is your air filter completely munged up?

Is your carb slide lifting all the way?

Did your buddy jam a banana in the tail pipe?

Check the intake cam lobes, make sure they're OK.

Take the head off, and make sure that the intake valves are actually opening all the way.

Sounds like it's not getting enough air. This would act worse at higher throttle settings. Figure out why, and you might fix the prob.

No KTM's, No banana's. LOL.

Intake tract is clean, carbs perfect, air filter is freshly cleaned. Seems to me more and more people are pointing at the head/valves. Ive never had the head of a 4-stroke off, kinda intimidating to me. Might be time to get out the book and get my hands dirty.

BTW, a few people have commented on grounds. anybody care to expand on this?

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