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Quick diagnosis help

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Saturday at Endurocross, my bike started acting weird. It would rev out just fine on the stand, but once under load, it struggled to get moving. There was no snap in the response on the bottom end. Eventually, the revs would get high enough and yes, everything felt just right, but not from a stop.

I am guessing clutch plates. It is a 2004 YZ250, with original plates and thousands of hours. I put the Rekluse in about 3 years ago and this is the first sign of trouble I have had.

Does clutch sound right? Something else I am not aware of? I am heading out for Thanksgiving and would love to ride on the riding weekend.

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Maybe 15-20, mostly low revving hours practicing EX. I am not concerned about that, I just did it over the summer and am not due until the spring or so, based on my typical top end changes.

Or should I be concerned?:lol:

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A worn clutch usually shows itself in higher gears. The load on the engine is lightest in first gear (just think how much easier it is to pedal your bicycle in a low gear vs a higher gear), so I would look at something else. The power valve is the first thing that comes to mind when power is poor at low revs but picks up at higher revs.

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A broken ring could to that to you IMO. Hopefully not but the age of the top end you OK for a YZ250 . I change it at 40 hours and ride it hard, quite nice broad trails.

I sure hope not. In fact, I doubt it, there was nothing to make me thing it was something in the jug. No rattling, no clanking, no loss of "perceived" compression.

Check that the PV is closing. I had one that broke and would not close, acted the same way. Good luck

I have no idea how to even check that. If I can't find the cure in the clutch area, I may have more questions for you.

Joe, check your Rekluse as well. I've had the small screws that hold the pressure plate on come loose and act like that.

You know Paul, I sort of thought about that. Knowing how the balls activate the clutch engagement, it did feel like it really needed to spin hard to fully engage.

Because I have to take the clutch cover off anyways, I just bought some new plates to swap out. I sure hope that cures it. Either way, after all these years, I figure it wouldn't hurt to put some new plates in. At least that way I know I am good until 2020.

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Hmm, now I am left wondering. I just put the new plates in, but the 8 that I took out were not bad. Spec is 2.9-3.1mm, and all the ones I took out were right around that. Before I did that, I fired it up (cold oil) and it had no problem grabbing.

Hopefully I don't find out it wasn't the clutch in the middle of a ride this weekend, 15 miles from camp.

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Like I said, a worn clutch will first start to cause problems in the highest gear, not the lowest. That's your first indication that it isn't a clutch problem. Check your power valves because if they are stuck open it would cause poor low rev performance. This is even more likely if you didn't clean your PV's during any of your top end rebuilds. Could also just be a clogged pilot jet....

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I had a problem very similar to this with a JetSki that I had done some work on. Out of the water it ran fine, under load it bogged and barely moved. Turned out I had swapped vacume lines on the fuel pump.

If the bike isn't reving under load then it's probably not your clutch as a bad clutch would let the bike rev more. I'd be looking for fuel delivery issues such as a clogged fuel line.

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