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Cause of 2-stroke revs dropping slowly?

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Hi I'm trying to get an old RT100 engine running right for the offspring. When I start it the revs are kinda slow to climb and very slow to drop and I'm wondering where to look for the cause.

The air box is missing and I'm guessing it was never re-jetted but other than that everything looks ok. Bore is brand new and no missing/leaky cylinder gaskets. Oh and the clutch is stuck so I haven't tried riding it yet.

So.. How to go about troubleshooting this monster? I've never come across this slow dropping revs thing before.

Thanks,

Jon.

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Old two stroke motors have very slow rpm reving to begin with.

Nothing like the precision two strokes from 1984 on.

On an RT 100, the engine will drop back to idle after a good whack in about 3-4 seconds.

If the idle actually hangs and then drops, you have an mis-adjusted air screw (start with a very low idle and raise it with the air screw) or an air leak.... OR  no airbox, which means no lengthened venturi after the carb, so it will run very lean, and slow.

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+1,   idle hanging high too long is lean from a mix screw or as slide adjust high (the idle screw), or combination of each.  Hopefully not from a seal leak.

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I was wondering about leaky crankshaft seals actually as the mains sound pretty rough. What kind of symptoms do leaky seals give?

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I was wondering about leaky crankshaft seals actually as the mains sound pretty rough. What kind of symptoms do leaky seals give?

 

One side will give you hanging idle and no top end

The other side will give you quick fouling plugs, mung and drool at the pipe, and no top end

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