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08 wr250, crook mid throttle

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Ran fine last week, took it out today, and it idles and revs hard fine, but mid range it is missing and un-ride-able.

No mods or changes since last week, do we assume a dirty jet or similar?

Was getting low on reserve, maybe pickup a bit of crud or water near the bottom of the tank?

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Could be.

Try draining the carb bowl via the drain screw at the bottom.

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I don't mean to jack a thread, but the exact issue has happened with my 2012 WR250F during a hare scramble race this past Saturday.  Only happens when the bike is at operating temps and at high idle (1/2 to full throttle).  It sounds like the bike is misfiring or on the rev limiter way too soon, and I do not have the power I know she has.  I ran her off of a separate tank of 93 octane from a different gas station (thinking that water in the fuel all of a sudden), and she still had the same issue.  Disconnected the TPS, checked main and pilot jets, checked float bowl (found nothing), replaced spark plug (found to be a little black on the electrode, but still working and within the gap specification range), and still the same issue.  My plan of attack is to check any and everything within the carb, which I should hopefully have something to report on within the next couple of days.  Very strange, as she has ran fine for over 2+ months since I got her.

 

From all that I can think of and talk with some other folks, its either fueling (carb) or electrical.  I am heading more towards carb being the issue.  I have a short video and will try to post it on youtube soon.

 

I will keep an eye on this thread and respond with anything that I find !

Edited by chittyrox

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Here is a vid of the issue.  She almost sounds like a 2-stroke when it happens.  is this something similar to your issue ?

 

Edited by chittyrox

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yip thats it, but I drained the carb via the big plug at the bottom, and found a reasonably large piece of dry grass with the small seeds on the end of it, and hoping that was just floating around under the main pilot... i will post in a day or 2.

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After checking everything inside the carb and cleaning it out, there was no issue found within the carb and she still had the issue after I fired her back up.  I pulled the coil and measured the primary and secondary resistance hot and room temperature (R.T.):

 

Primary Hot --> .09 - .3 ohms

Primary R.T. --> .3 ohms

 

Secondary Hot --> 6.2k ohms

Secondary R.T. --> 6.2k ohms

 

The spec, per the 2012 WR250F manual, is:

Primary at 68 deg F --> .08 - .1 ohms

Secondary at 68 deg F --> 4.6k - 6.8k ohms

 

I have a replacement coil on order, and I can only hope that the CDI isn't damaged either as it is ~$300 !!!  The way the primary coil measured out, that would explain why it only happened at high RPM's.  I may not get the coil until sometime next week, so I will update once I get that part replaced.  In the meantime, it's on to riding the WR450F or the DRZ400S on the trails !!

 

- CR

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I gave the carb a small clean without taking it off the bike, but it still does the same thing.

Runs fine on choke, not without choke, so it's going to have to be a full strip and clean jets etc...

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Sounds like a plugged pilot jet and related passages.

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I gave the carb a small clean without taking it off the bike, but it still does the same thing.

Runs fine on choke, not without choke, so it's going to have to be a full strip and clean jets etc...

Did you remove your headlight from your WR250F ?

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no, why is that?

I dug abit deeper and found some posts of this happening after removal of the headlight, which was exactly my issue. Put headlight back in and problem went away. Headlight out and issue happened. Reports showed a stator issue, but even mines would charge within voltage specs at 8k+ rpm's. Only reason I don't want the headlight in her is because of going down and possibly breaking it during a hare scramble race. Found a slight work around, which is more of a band-aid but its worked after 8 races since & the issue has not returned for me. There was absolutely nothing wrong with my carb nor fueling. I have a spare regulator and stator awaiting to be installed over the winter.

Your issue seemed to be more of fueling, but was your issue resolved after carb cleaning ?

Edited by chittyrox

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07 Wr250f, I have the same problem. Headlight blew, bike would sputter during acceleration, half to full throttle. Replaced the blown bulb, ran fine. I have read that the problem is with the regulator rectifier. Not sure if I should replace it or just run it until the new bulb blows. New rec reg is $130. Aftermarket on ebay start for about $35.

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