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02-13-2015, 03:23 PM

#171

MJD

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Quote:

Originally Posted by GREG DOE

I believe there is some misinformation on the Perry Pump, and Perry Pump Carburetors. The original Perry Pump is an oscillator pump. It works on vibration. There is also a Perry Pump that replaces the engine rear cover, and that pump works on regulated crankcase pressure. The pump carburetors have a larger bore, so that more fuel, and air can be ingested. For a given engine, the pump carburetor wouldn't work on suction. Not only would the mid-range be a miss-match, but there would be insufficient fuel draw at wide open. Greg

I was referring to the VP-30 regulating pump. There still is the VP-20 oscillating pump, which is geared towards 4 cycle engines with the larger amplitude vibrations, but is used also on two strokes AFAIK.

But the pump carbs do I think have some feature that cleans up the midrange, not just a larger bore? Otherwise you could just swap in a larger carb. Jett tweaks the midrange with the cam profile on the throttle barrel, and Fox did also according to Jett.

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