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PLEASE HELP! MAJOR STUTTER 05 CR250, replaced CDI & Carb/jetting

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Ok so I am having  a huge problem that neither I or a friend who works on bikes can figure out. I have a 2005 CR250 that was running great then took it out and started loosing power. So the bike starts 1st or 2nd kick every time and when you pull off it runs great until it gets into higher RPM's where it gets a MAJOR stutter. the mechanic friend found that when you run it then shut the gas off it seems to run a little better as it runs out of gas if that helps. Just put in a brand new CDI box thinking that was the problem and that's a no go. Then I bought a new JD air striker pwk Carb with JD jetting thinking it was a jetting/ carb problem and no go.. same issue.. he checked the reeds and all looked good. power valve seemed to work fine but if I know correctly now that I have changed the carb it takes out the TPS since its unplugged.. changed the Plug 3 times so not that either. running 32:1 gas so that's not the problem.  ANYTHING will help at this point... Thanks in advance !!!

 

 

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Have you check the muffler core for a possible blockage?

What's your air filter like?

When your friend checked the reeds did he pull the whole reed block out and look inside at the intake side of the piston for any damage?

Take off the pipe and look inside at the exhaust side of the piston to rule out anything major.

It could be a few different causes but if you start eliminating them one by one you will find the problem?

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There's a chance the float level is too high, resulting in too much fuel for the bike at once.

I had this happen on a cr 250 (could happen to any bike) and more or less it had the same symptoms a you've described.

It would bog and lose power very badly unless it was absolutely wide open. Meaning: I was utilizing the fuel supply.

The fact that you said it runs a little better when the fuel is shut off leads my mind to this a possible cause of your symptom. Almost like its drowning with it on.

Anyhow, if this ends up being the cause, all you need to do is (very very lightly) bend the tang that the needle valve rides on between the floats. If you bend the tang up^^ then the fuel will shut off flow into the float bowl sooner.

Your manual will give you the proper float height in millimeters.

It's common to bent the tang on accident while jetting, or inspecting a carb.....Or even making a sudden grab as that stupid float-pin falls out and you try to catch it all before it hits the floor! Haha-

I'd suggest this "free" inspection before you spend anymore money. Sounds like you've wasted enough! If you can get all your bikes specs in order it will always be on point! Good luck!

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Ok so just got back to the house... Checked the muffler all looks clear and in great shape, air filter is new, no dirt/mud or the infamous rag. When he pulled the reeds out he did it completely and checked the intake side of the piston which he said looked good as well as had the full exhaust off and checked in there. All great tips to check and def. trying to knock out possibility by possibility....

 

the problem started with the stock carb before I switched to the air striker so don't think its a carb/float issue since its the same issue on both carbs. I just ordered a rectifier regulator on Ebay to see if that may help.. Any other help would still be greatly appreciated...  Thanks guys/girls =)

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Man all that stuff you've replaced rarely ever goes bad..Do you know for a fact that your powervalve is operating properly?

Yea I agree, honda electrics are pretty good!

The only weak link maybe the killswitch? Try disconnecting that

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Guess you could have a short...doesn't hurt to check. Bare wire somewhere grounding out... I need to read your initial post again

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pretty sure the power valve is working properly, we opened the cover on the RC valve and when we give it gas it moves up and down which leads me to believe the servo motor is working right. it does get a little studder at the high end of the rpms but figured that's due to the problem I cant seem to find.  tried disconnecting the kill switch as that was a past problem on a 00 kx250 I had.. guess I can walk through all the wires to see if anything looks out of place shorting out.. Becoming more frustrating than anything... Thanks again !

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Have you checked the spark plug wire ?  You mentioned it starts 1st or 2nd kick but loosing power,  Is it a fresh topend ?   Another thing to consider is bad gas if it's not a fresh mix.    

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Ok so I am having  a huge problem that neither I or a friend who works on bikes can figure out. I have a 2005 CR250 that was running great then took it out and started loosing power. So the bike starts 1st or 2nd kick every time and when you pull off it runs great until it gets into higher RPM's where it gets a MAJOR stutter. the mechanic friend found that when you run it then shut the gas off it seems to run a little better as it runs out of gas if that helps. Just put in a brand new CDI box thinking that was the problem and that's a no go. Then I bought a new JD air striker pwk Carb with JD jetting thinking it was a jetting/ carb problem and no go.. same issue.. he checked the reeds and all looked good. power valve seemed to work fine but if I know correctly now that I have changed the carb it takes out the TPS since its unplugged.. changed the Plug 3 times so not that either. running 32:1 gas so that's not the problem.  ANYTHING will help at this point... Thanks in advance !!!

 

 

My CR125 did this, it was caused by a blown flywheel side crankshaft seal.  It was causing a rich jetting condition which caused the stutter.  Once I replaced the seal the problem was solved.

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My CR125 did this, it was caused by a blown flywheel side crankshaft seal. It was causing a rich jetting condition which caused the stutter. Once I replaced the seal the problem was solved.

Left side would equal lean condition

I suspect it's the right side crank seal and suggest replacing both crank seals

2 tips

1. Get the OEM seals

2. Us PC seal grease on the lip of the seal and red lock tight on the outside of the seal is cheap insurance against air leaks

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Left side would equal lean condition

I suspect it's the right side crank seal and suggest replacing both crank seals

2 tips

1. Get the OEM seals

2. Us PC seal grease on the lip of the seal and red lock tight on the outside of the seal is cheap insurance against air leaks

Good point I had forgotten this as a possible culprit .  1 of my 93 CR250's had a bad Rt. side crank seal & had sysmptons as described.  It did sputter from mid to high rpm.  

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Left side would equal lean condition

I suspect it's the right side crank seal and suggest replacing both crank seals

2 tips

1. Get the OEM seals

2. Us PC seal grease on the lip of the seal and red lock tight on the outside of the seal is cheap insurance against air leaks

 

You would think.  I don't know why it did it but it was the crank seal.  I kept leaning and leaning out the jetting until the bike started pinging.  My only explanation is that somehow it was creating a vacuum pulling more air through the carb making the motor think it was running rich.  replacing the flywheel side crank seal fixed the issue and my jetting went back to normal.

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