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Littlefoot

Measuring Vacuum

7 posts in this topic

Has any body tested with a vacuum gauge on there bike? Where did you attach and what were the readings?

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Originally posted by Littlefoot:

Has any body tested with a vacuum gauge on there bike? Where did you attach and what were the readings?

Never, but how about plumbing it to the hot start circuit?

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I just did the same the other day out of curiosity...

tame the fluctuations by slowly pinching the hose until the needle only wiggles a little.

What you get is repeatable, but I don't know how useful???

My readings were 10-11 in.Hg vac. 11 when idle was on the verge of stalling, 10 or a little less after turning up the idle screw a bit.

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That's what I thought. I attached the vacuum gauge hose to the head side carb bell nipple, where my hotstart is attached. Wild fluctuatuions at idle.

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surely vac guages are only any good when comparing two carbs or more?

have i missed something here?

Taffy

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Typically I would use gauge for indications of valve / valved guide / piston ring condition. Just an indicator mind you. Then if there was cause move on to compression and leakdown testing.

It's just a quick and easy check to throw on a vacuum gauge. Could be any thumper has the fluctuations, never tried one before, just curious.

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