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06 rm250 won’t rev out or sputters on top

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My son’s 06 rm250 is all stock and we have owned it for 3 years. Before last race about 3 weeks ago I had to do some tranny work to it so I put a new piston in while it was apart. It ran fine and no problems and has sat in the garage until this past weekend when we headed to silver lakes sand dunes. The only thing different was we put an outer wears pre filter on it. When we got in the dunes it will not top out, above half throttle it sputters and bogs. It has a 168 main so I tried a 170 and it still did it. It will do it in neutral free reving it, so I did reved it a few times and pulled the plug and it was wet. So i wondered if the choke is stuck, but when its idling and I pull the choke I can tell the choke is working. So I put a 165 main in it and still the same thing. I pulled the prefilter off and still the same. We tried a brand new plug and still the same. We gave up and brought it home. I put a new dry filter on it to make sure it wasn’t starving for air from filter oil and the same thing. I checked the timing, I checked the power valve, the carb slide is opening all the way, the jets are clean and bowl is clean. Then I started it back up and was reving it and it was still doing it then it started reving up nice and clean. I shut it off and went to restart it and it wouldn’t start because I found I left the gas off from checking the carb. So I turned gas on and started it and the sputter and bog was back half throttle or more almost like the choke is left on. From this I am figuring it is rich but already went from a 168 to a 165 main. I am thinking of trying a 160 main, but in three years I haven’t had to mess with the jetting why is it so off now? the plug has always been nice and tan with the 168 main

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I'm not sure whats wrong with the bike, but all I can think of is to make sure all the vent hoses from the carb are not stopped-up with mud or crud,,,,,I know My RM did some weird stuff when that happened to Me,,,,,let Me know what You find..........Dr.D..

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reeds look good, just the white inner plastic cage comes right out if I tip it. Its not tight in there, but the reeds are not broke or anything

going to check the choke, but I have checked everything else I can think of

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pulled the choke plunger out and it looks fine seems to be working, sprayed all the carb vents out, cleaned all the carb circuits out, pulled the needle out and its on the middle clip. put the original jetting back in main 168 and its still doing the same thing.

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maybe bad or wrong spark, measure coil, cdi, ..

i've had my choke stuck once, it looked like it was down, but it wasn't totally

result

really hard to start when hot, lots of spooge on the beginning of my exhaust, not reving

it was idling fine, and in neutral it would rev just fine

also i've had a worn powervalve system, it would rev fine in neutral, started good

ran good in lower rpm, but wouldn't rev out, right powervalve was worn, the little rod with the grove in was totally worn and wouldn't turn out anymore

other thoughts, bad crank seal? bad gaskets?

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Tried new plug already, went down to a 152 main and it revs a little crisper but still not right. Even tried swapping coils including boot with our 125 and still the same thing. How would an air leak with gaskets require less fuel to rev out? This is what has me puzzled. The only other thing I just thought of is I put a screen in the stock silencer for the sand dunes as a spark arrester. I am wondering if this maybe the problem or some how causing an exhaust blockage. I am going to pull the screen later today.

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Oh also had both sides of power valve apart and have rechecked and checked power valve preload and operation over and over

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Yes, definitely try pulling the screen - but put the 168 main back in before riding it, the current 152 would make it dangerously lean.

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Ok pulled the screen, thought it was the problem for sure because the top edges of the screen had some packing around them. It is still doing the same thing. Here is a video, it is back to the original 168 main. let me know if it doesn’t play

http://th_2287E208-0786-45E2-81F5-32A6B9CFA632-6840-000003E654DC644A_zpse7ab9045.jpg

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It Played,,,,,,,,,is Your throttle cable adjusted right,,,,,a longer video would be better,,,I'll be curious to find out what the problem turns out to be,,,We might learn something from Your bad luck.........Dr.D..

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I recently put a new throttle cable on it, but the other day I check and the slide is opening all the way.

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any other ideas?

If you hadnt used the pre filter before, take it off, may be suffocating the engine? If it is oiled, as well as filter you could be sucking filter oil which will make ur plug look wet and the stuff has a high flash point like premix oil. It also could have creamed your main jet up a bit and made it run lean

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Sounds like a bad cap or coil to the spark plug. I had the wire break to the cap and it would run OK until it was wide open. I just cut the wire and epoxied back into cap and it was fixed. Coils can be weird. We had an rm80 that would miss at high rpm and the coil would short intermittently.

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I have a dry filter no oil and no per filter now and it's still doing it. I swapped coil, wire, and cap with our 06 rm125 the other day same thing. Plug is new and tried a different used one. Had the head off last night everything looks norm and power valve is working. Tried the Cdi off the rm125 still the same. Tried unplugging the solenoid on the carb, no difference. Tried moving the clip up one to the second notch from top, No help. Tried flipping the reeds, no difference. At a loss.

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Clean ground? Stator? Maybe pull the wiring harness and check for corrosion or breaks hiding under the loom.

Edited by tnrider013

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IF it revved perfectly when the fuel was off, But started acting up when the fuel was back on. I would be hunting down a carb problem. Check the float height, and the needle valve in the float bowl. IF you found packing of any kind in that screen. Repack the silencer as well.

Sounds dumb, but my yz250f would do something similar, after half a day of testing everything. turned out tobe a bad kill switch. Disconnect the kill switch.

* just watched video, the power valve is what gets my vote. its not opening properly. The power valve governor, or the valve itself. when You did your top end you messed it up somehow.

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