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i have recently picked myself up a wr250f 2004 and seems to have an electrical problem. rode fine when i got it after about 30 mins into the ride it seem to splutter in the lower rev range or when engine was loaded up seem to clear up in high revs (not much engine load). after a few more minutes bike started to be impossible to ride back firing and just bogging right down till it stalls. done the normal checks cleaned carb, new fuel, checked spark, checked air filter ect. at this point it would idle quite rough and noticed would stall when high beams are on (lights are on when bike is running all the time). checked voltage from battery it was sitting at 7.5v and when bike is running drops to 6.4v. I jumped it using a car battery and idled perfectly and revved just fine. i charged the battery up and managed to bring it back to 12.6v. tested voltage again and seem to not be charging at idle revved it up to about 3000rpm and nothing happened straight away then seem to jump up to 13.1v so i assumed the charging system was okay and it was just a flat battery causing my issue.  went for a ride approx 6kms or so and ran good. votage stayed at 12.6v with bike off. next day took it out for a slightly longer ride and started to splutter again. turned around and got half way home until bike was once again unridable. voltaged seem to be at 12.5v. 

i am pretty comfortable working on cars but very knew to bikes.

so my thoughts is that bike is some how not giving the ignition system enough power to run correctly. cutting spark in and out causing it to bog and back fire? my understanding is that the stator generates ac power to power the lights and ignition system and charge battery (once converted to dc). if the stator is at fault would my lights not cut in and out also? 

sorry for the long post just trying to get some insight from people with more experience or maybe someone has had this problem before. done a little bit of research but couldnt fine to much.

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Battery voltage, not running should be 12.5v; running should be 14v.  How old is the battery?  If its over 3 years old, should be replaced.

Otherwise, it sounds like its not charging.  I'd pull the left side cover and check the stator and flywheel.  Looking for debris in there, stuck on the magnets, and for cuts to the wires.  Make sure the mounts are snug and nothing is moving around where its not supposed to.  Then check where the wires come out of the case for cut wires, especially at the grommet, then up the frame to the connector to the wire harness.  Assuming that's all good, could be the regulator/rectifier.  The manual will give you points to check voltages.

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I have burned threw two regulators/rectifiers on my 2003 wr250f. One was less than a few weeks old. My headlight bulbs would burn out and I would have 25 volts at the light switch. The bike would still run however. I agree with the above poster. Sounds like a stator or battery problem.

Edited by Jay762

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Once you get a new battery, look for the grounds, and clean them up and reattach.  Then check for the stator to be loose on the left side under the cover.  If its loose, make sure the flywheel is not loose.  Beyond that, just go thru the wire harness and clean the connections.  The bulb socket are next; check and make sure the bulbs are tight.

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Cheers for the help. After doing some resistance checks on the stator and what not I found out it was just one of the pins on the coil itself to be bent slightly up contacting the coil plug intermittently bent it back down so now it actually fits in the terminal properly. The whole battery thing must of just been a fluke. 

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