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02 CR 250 issues

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I bought this bike last year for dirt cheap with what wound up being bad main bearings. I put new bearings/seals/top end in over the winter. Fired it up and realized it was not getting into the powerband. Looked at the RC valve and realized that the cables were in pretty bad shape. I had ordered the new cables, but kept playing with the adjustments to see if it would run any better. I ran it up and down the street a few times and it was still not getting on the pipe (bottom end nice and snappy). While coming down the road it just quit on me abruptly. Kicked it over a few times and the motor turned without issue. I kinda figured that I fouled a plug since the ex valve was not opening and the plug was probably getting loaded up. Since I did not have a spare plug, I put it up and figured I would mess with it after I picked up some new plugs and got the new RC valve cables. So the cables came the other day and I put them on. I noticed that the old return cable was really frayed and difficult to get it to move through the cable cover by hand (which I think was the issue). So I adjusted the cables per the Manual, and dropped a new plug in. Kicked it over a few times and she fired up briefly (1-2 seconds), but then it shut off. It did this a few more times, almost seemed to be starving for fuel. When it would fire, if I gave it some throttle, it seemed to keep it running for maybe a split second longer. I checked and there is plenty of fuel in the tank. Any ideas? The abrupt shut down when riding makes me think that something went awry all of a sudden. I am not really good at diagnosing 2 strokes, so I am kinda confused about this one.

2002 CR 2502, new top end, stock TMX carb with a 400 main, 32.5 pilot (as I remember), stock needle 3rd clip from top, stock pipe and silencer, CF reeds.

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Damn...Nobody has any clue? I was thinking the stator or maybe the ignition coil? Anybody else have an idea?

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I'm curious about one statement you made, "if I gave it some throttle". I have an 07 CR250, and if I don't give it some throttle, I can't get it to start at all, and if I let go of the throttle, it won't stay running...

The way I start my bike is to put it in neutral, pull the choke, then slowly kick it over twice with the throttle completely closed, then I open the throttle a good ways and give it a good kick and it always starts...

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The symptoms you describe when it was running (not hitting powerband but snappy bottom end), sounds like your exhaust valve. take the cover off the left side of the cylinder and see if the shaft is rotating from L to H when you rev the engine. not sure about your sudden stalls though. maybe give the carb a cleaning.

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and Dougster makes a good point, a lot of 2 strokes are set up to stall if you're not on the throttle, even more so if it's not warmed up yet.

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Since I put the new top end in the bike, It starts 2-3 kicks always and idles fine. The butterfly for the Ex valve moves freely by hand, so I am convinced that the cables were frayed to the point of not allowing the servo to push/pull them. I am pretty sure that I fried something when it shut off on me. All of a sudden, it just stopped like someone hit the kill switch. What would give this response? Coil went bad?, stator fried?, Cracked reeds? It did not stall like when it would run out of gas, It just quit on me like something went bad!

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You could try unscrewing the plug, reconnect the plug wire and put it on the top of the engine to make an electrical connection, then try turning the engine over and see if there is a spark...

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You could try unscrewing the plug, reconnect the plug wire and put it on the top of the engine to make an electrical connection, then try turning the engine over and see if there is a spark...

That will be my 1st look. Although I need an extra hand kicking it over while I watch the plug (arms are not long enough to do both!:smirk:).

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Late update......:smirk:

I finally got around to messing with the bike the other day, had plenty of spark, plenty of compression, and plenty of fuel.....It would even run for a few seconds if i had WFO throttle when kicking it....pulled the top end, and found out the lower con rod bearing took a shit:banghead:

anyways, pulled the motor apart again and sent the crank to Cooksey Cranks in Texas....waiting to get it back for the re-re-build.....:p

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Thanks for the update. That could help someone else diagnose a problem later on....

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Thanks for the update. That could help someone else diagnose a problem later on....

In hindsight, I should have had the crank rebuilt while I had it apart the 1st time, but there was no up and down play in the lower bearing. Oh well, live and learn:bonk:

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