Perry pump instructions

[Dean Pappas]

Hello Paul,
What John told you is quite correct, and as others said, the pump gets richer when the screw is turned in (clockwise.
The reason that I'm throwing my two cents in is to give you the general procedure. 

here we go: 
First approach ...  run the engine with suction feed or muffler/pipe pressure, and get a needle and idle setting. Then turn the needle in a "bit" and attach the pump and adjust it so that the top end mixture is about right. 

Alternatively, you can set the neddle to two turns, say a prayer and twiddle the pump until the mixture is about right.

Then you get the idle and top end mixtures very close to correct, and check the mid-range mixture ... If it's rich in the middle, then lean the pump, and reset both the top end and idle and keep repeating until golden brown. The best way to check the mid throttle is in flight: mid-range hysteresis usually meand that it is rich. What I mean by this is that pulling back from W.O.T. may give a different power setting that than the same stick position when approached from low RPM/low speed/cool operation conditions. (Cool operation is like after a spin.) A lean mid-range leads to pinging on the throttle-up for verticals or inexplicably blown glo-plugs. Sometimes you'll even hear what sounds like a backfire, on throttle-up, if either the middle or idle are lean.

The principle behind all this is that the pump affects all throttle settings, while the main needle dominates at W.O.T. and has less and less effect at lower throttle settings.

Hope I helped,
	Dean P.



-----Original Message-----
From: Paul Horan [mailto:phoran at vvm.com]
Sent: Wednesday, April 21, 2004 1:19 PM
To: discussion at nsrca.org
Subject: Perry pump instructions


Hi,
    I am planning to use an old perry pump on a OS91FX, only problem
no instructions on the perry pump.  Can anyone advise me on adjusting the
pump.  I will be using crankcase pressure, but do not know how to 
adjust the hex nut on the pump.
Thanks,
Paul
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