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1984 dr250 misfiring at high rpm

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Hi i have a 1984 dr250s that im restoring that misfires always just at 4500rpm and 8000 to 10,000rpm but wont rev out enough without misfiring/ignition breaking up to get to 10,000rpm. Any other rpm it rides fine

It has a new stator, coil with lead, plug, plug cap, crank position sensor, cdi, spark plugs, battery and charge rate are good, has new carburetor and manifold

Im really dumbfounded on what it could as it starts good hot or cold just at those rpm it really misfires badly

 

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Does this happen mainly when at speed? Because it sounds like the carburetor vent is getting some turbulent air.

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Even just free revving it in neutral it breaks up at those rpms

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So ive replaced the spark plug, cdi and coil with known good ones Ive checked the coil and lead, spark plug cap, coil pickup resistance which are all in spec cold or hot. Battery and charging system are good, grounds good But when ive checked resistance on the stator coils low speed are in spec but the high speed stator coils resistance is higher than the spec, could this be my issue causing my high rpm misfire?

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How far out of spec are they (hi speed coil)? If it's just a little (don't know the factory spec to give an example), could be meter error. Also, check your ingnition components while cold AND hot if you can (edit: sorry, missed that you already did that). It's not uncommon for ignition componeynts to test "serviceable" while cold, but then have a significant increase in resistance while hot (coil caps and often pick up coils being a prime example of this).

Edited by mentolio

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