Yz250 starts but bogs and shuts off

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1/22/2020 9:13 PM
Edited Date/Time: 1/22/2020 9:19 PM

I have a 2011 yz250 i use as a woods bike. I noticed the other day it started to get just a split second lag in power when i get on the throttle. I took the carb apart and the pilot was a little plugged up. I cleaned it out and even jetted it with a 45/172 to lean it out a little for woods. I rode it a day and it still did the same thing. Next i took the v force 3 reeds i had in out and put the stock back in just to see if maybe the reeds were going bad. I rode it up the yard and it bogged and shut off. It would start back up but only run for 30 seconds or so. I took it all back apart and put the vforce back in it and swapped out a few petals that were getting worn. Now the bike will start and bogs real bad and then eventually shuts off. When it shuts off it back fires almost every time. The plug is always wet when i take it out. I know this jetting isnt the problem because i have another bike with the same jetting. Also a slight adjustment wouldnt make it this bad. I tried taking the powervalve linkage cover off and it looks to be moving right but could there be something else with the powervalve wrong? Or any other ideas? Thanks

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1/23/2020 2:02 AM

Did you split the entire carb or did you just pull the jets?

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1/23/2020 6:02 AM

Just pulled the jets

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1/23/2020 6:58 AM

Did you check your float , needle and seat?
Did you check your fuel tank petcock filter?
When was the last time the crank seals were changed?

Paw Paw

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1/23/2020 7:01 AM

Did you use paper towel or rag to plug airbox for debris, sound like restriced air flow? Double ckeck jets did not unscrew?

All guesses

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1/23/2020 7:05 AM

Paw Paw 271 wrote:

Did you check your float , needle and seat?
Did you check your fuel tank petcock filter?
When was the last time the crank seals were changed?

Paw Paw

I did clean the filter in the petcock and the crank seals have never been done that i know of. I bought it used with not many hours on it. Ill check the float and needle today

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1/23/2020 7:06 AM

kijen wrote:

Did you use paper towel or rag to plug airbox for debris, sound like restriced air flow? Double ckeck jets did not unscrew?

All guesses

I thought of this also because i did have one where the reeds go while i had it apart but i know i took it out. Im gonna double check though just incase maybe a piece got stuck or something

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1/23/2020 9:01 AM

Check your powerjet if the bog is related to throttle position at all. It's the one which points forward into the venturi from the back of the float. Also, make sure the throttle position sensor is properly engaged.
Mine has never had a problem, but I hear that setup can wreak havoc on your jetting if it's off.

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Braaapin' aint easy.

1/23/2020 11:46 AM

This sounds like it might be electrical to me. Jetting doesn't "go bad". If it's running good and then it's not you shouldn't need to adjust jetting for that. Sounds to me like the stator is getting weak or there is a bad connection in a wire or the plug wire/cap. Check coil mounting and ground to frame. Remove the ignition cover and make sure there isn't excessive corrosion or moisture in there.

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Powerband in every gear !

1/23/2020 1:34 PM

Paw Paw 271 wrote:

Did you check your float , needle and seat?
Did you check your fuel tank petcock filter?
When was the last time the crank seals were changed?

Paw Paw

Lesko34 wrote:

I did clean the filter in the petcock and the crank seals have never been done that i know of. I bought it used with not many hours on it. Ill check the float and needle today

Plan on replacing the 9 year old crank seals as well. They are not hard to change even with the engine in the bike and the cost is very low.

Paw Paw

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1/23/2020 8:38 PM

Thanks everyone. Finally figured it out after days in the shop. The power valve has a stopper on it that when it fully opens it stops against the cover that is on the front of the cylinder. Well the stopper which is pretty small broke off and was stuck under one of the cam looking things (called pulleys i think). Only thing now is that i have to buy the whole power valve which is $180 because the stopper is permanently attached to it

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1/23/2020 8:40 PM

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