Vacuum pipe question?

mr.z · World Chat Champion Joined: 04 Feb 2004 Karma :

Daft maybe but.. what does the vaccum pipe from the tank to the carb do??

Its connected to the tank, while attempting to balance the carbs (imopssible without the tool Rolling Eyes

) it was suking air into the carb, every couple of seconds (at random) it would go >PFFFT!< the revs would drop a bit then build up.. put a glove on it and it sort of ran normally...

Just wondering really.. Neutral

I guess it might pull more fuel through wne its needing it? or open a valve on the tap to allow more through??
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0ddball · World Chat Champion Joined: 15 Jul 2005 Karma :

The idea is that when the engine runs the vacuum in the pipe pulls on the diaphragm in the fuel tap and lets fuel flow. Hence no fuel should flow though the tap unless the engine is running.

When balancing you should block this pipe off and either use the prime position on the fuel tank if it has one or rig up a temporary fuel tank.

Bezzer · World Chat Champion Joined: 14 Apr 2005 Karma :

The carb causes the vacuum in the pipe which opens the diaphragm in the petrol tap allowing fuel to flow from the tank to the carbs. No vaccuum = no fuel flow that's why you don't have an "Off" position on the fuel tap.
When balancing the carbs you should either use another fuel supply or run it on Prime and block the vacuum line as it can give a false reading.

edit. snap, too slow a typist Mr. Green

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mr.z · World Chat Champion Joined: 04 Feb 2004 Karma :

Thanks guys, makes sense.. mine does have an off :o but that makes sense... the original cx didn't have a vacuum and would have problems flooding if left for a week, this explain why i think...

I set up a very clever arrangment with a fuel hose, funnel and bungee's on the garrage celing Razz

worked great...

Thanks for that Thumbs Up

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stinkwheel · Bovine Proctologist Joined: 12 Jul 2004 Karma :

mr.z · World Chat Champion Joined: 04 Feb 2004 Karma :

Yeh i was carefull about that, it wasn't diectly over it (half a bikes length away, it was only full to the point i could see the fuel and the fire extinguisher was right next to me Laughing

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