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200R Rev Limited

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So I've rebuilt the top end on my '87 after cooking the last cam. Got a new megacycle needle bearing cam, new rockers, R/D Springs, etc.

Finished assembling it, fired it up to break in the new cam and it idles fine. Problem is, when I roll on the throttle and spin it up over 3-5K, it sputters like its got a rev limiter on it. Let off the throttle and its got a nice, even idle.

We have an old shop XR that does the same damn thing: No guts over 5,000 rpm. Valves are adjusted, timing looks good, carb has been recently gone through. I'll give it another thorough once-over in the morning.

Any ideas?

Edited by krapfever
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You may have missed some dirt in the carb, or bad gas.

The search for the problem gets a little harder after you eliminate the easy fixes: Fresh spark plug, cut 1/2" off the plug wire so the adapter gets a bite on fresh wire, retension the timing chain (warm engine), check all electrical connections, disconnect the kill switch, clean the air filter, check the advance mechanism for sticking.

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Alright, I'm really baffled.

The motor will not rev cleanly above 3500-4500 rpm. Stutters like mad on acceleration past 3500 rpm and the revs pulse when the throttle is held at 3/4 open.

Where I'm at:

New Megacycle Needle Bearing Cam installed (Lift: .370" Duration: 273° Lobe Centers:102.5°)

XR's Only headpipe with a CRF230 can modded to fit.

R/D Springs, stock valves, Wiseco 66.5mm piston, stock carb.

Valves adjusted to spec., Ignition static and advance timing set, air gap set.

UNI foam filter (clean and oiled)

Carb cleaned thoroughly, new NGK plug installed. Good gas.

I have tried the needle at fully rich and fully lean. For some reason, it seems to like lean (?!?). I had a 115 main jet in there, dropped it down to a 112 and it seemed to make no difference between jets even with the needle at the leanest setting. With the 112 in there, I moved the needle to the richest setting and...same deal. I tried retarding and advancing the timing with each different jetting configuration: no change. Ran it with and without the air filter at each setting: nope. Ran it with and without the kill switch connected: yeah, no difference at all. Seems like the only change in this behavior that I can bring about is making it worse by richening up the mixture.

I'll check the connectors at the coil and cdi box again (both functioned fine before the cam swap).

Could the cam need to be degree'd in? I set it to stock timing because I don't have the adjustable cam gear.

I really don't know. I'll say again that we have a beat up '94 200R that's entirely stock and it behaves exactly the same.

I'm running out of ideas.

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