Measuring Vacuum

6 replies to this topic
  • Littlefoot

Posted July 12, 2002 - 02:58 AM


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

  • Hick

Posted July 12, 2002 - 07:05 AM


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?

  • Littlefoot

Posted July 12, 2002 - 09:08 PM


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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  • tbronc

Posted July 12, 2002 - 04:43 PM


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.

  • Taffy

Posted July 12, 2002 - 09:54 PM


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

have i missed something here?


  • Dan_Lorenze

Posted July 12, 2002 - 11:19 PM


[ July 13, 2002: Message edited by: Dan Lorenze ]

  • Littlefoot

Posted July 13, 2002 - 02:39 AM


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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