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Old Sep 29, 2006, 11:27 AM
Jeffery is offline
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And You're Not
Timbuktu, Mali (Happy?)
Joined Oct 2002
6,514 Posts
There is no pump on a YS .91. The crankcase pressure pressurizes the fuel tank, the check valve keeps the tank pressure from going back into the engine. The tank must be pressurized for the engine to run. What you might be mistaking for the pump is a pressure regulator, it simply meters the pressurized fuel going to the carb.

The easiest and best way is with a T in the line between the tank and check valve on the "vent" line and anywhere in the pick up line. I don't like the fuelers, a YS doesn't just need "some" pressure, it has to maintain "exact" pressure or the regulator won't function properly. Even a miniscule leak in the fueler will cause headaches, the simplest method is the best (I don't even use the T, I just disconnect the hose from the check valve to let the pressure off to fill the tank).

Oh, and the "supercharger" has nothing to do with the pressurized fuel system. The YS can keep a slightly higher than atmospheric pressure on the intake tract by using a disc induction and a carb that's divided in 2 parts separated by an o-ring on the carb barrel. Again, it's just a clever way of using crankcase pressure, there is no actual "supercharger" mounted on the engine, just like there is no discreet "fuel pump".
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Last edited by Jeffery; Sep 29, 2006 at 11:36 AM.
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