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1980 rm100 crazy rich w/proper jetting

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1980 RM100 case reed engine with Mikuni VM30 carb, all jets, needle, slide, float level are correct. Compression is 130 psi.

Bike will only start when cold and no choke. Try to rev it and raw fuel starts ooozing out both ends of the pipe, won't rev past about 1200 rpm. Idles fine when cold, but as it warms up it starts pumping raw gas spooge.

Moved the needle to top position, it helped a little bit, but not much. Next I replaced the S-0 needle jet with a much smaller P-0 and it actually runs well in mid rpm, but still way rich on the bottom.

So the question is, why? With the air filter off I don't see any indication of spitting back through the carb, as I would expect with a bad reed, or would that be that obvious?

Point me at some solutions.

 

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Float bowl height ? Is this set correct.

if the needle &%$#@! is at top position something is wrong 

is the engine in good condition 

How old are the reeds if you don't know replace them

stock jetting as per manual is a guide and will always be super rich

 

 

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Float level is correct and swapped in a different needle and seat.  It ran like this when I bought it, but with 130 psi compression I'd say it's in so-so condition. If it's not reeds I'm totally flummoxed. But if it's reeds it should be "pulsing" back through the carb, right?

 

 

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19 minutes ago, Bolon Yokte K uh said:

Wouldn't that make it run lean?

 

 

Left crank seal pulls in air

Right crank seal pulls in OIL.

You can tell by the taste/smell of the oil on the plug if it's premix unburnt or trans oil......but it's going to be trans oil, becuase you are getting a blue/white smoke, and the oil is not very sticky....

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Okay, I see what you're saying, but this thing is pumping gasoline. Gotta say it runs good when I put in such small jets that it shouldn't run at all. I did have a KX suck trans oil from a crank seal, so I know what you're talking about.

 

 

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Time for some new crank bearings sounds like. Witch causes the seal to leak :thumbsup: new seal may work for bit but not permanent fix

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It's 37 years old. Unless it's recently been fully rebuilt its whooped.  That's your problem :ride:

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