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Getting this perry pump working, arrgh!

I have a perry pump setup on my O.S. .46FX. I use it for a large 24 oz. fuel tank located at the cg, this is a duration type model. My problem is the mid range. No matter where the hex nut adjustment on the pump is set, the mid range is very rich. The engine idles well and the top end is fine, but nothing I do prevents the mid range from being so rich that any time spent there just bogs the engine down a lot. The carb is a double needle type, just like the pump instructions call for. Any suggestions?

Reply to
Frank Costa
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Get a Perry carb. that is calibrated for the extra fuel pressure and it will have a good mid-range

Reply to
Flierbk

I'm assuming this the pump that uses a tube off of the engine crankcase to work and it is not the oscillator type.

As you may already know the hex nut sets the fuel delivery "pressure". Once you've set it such that the carb controls the fuel delivery and not the pump, you then adjust your carb's high and low speed setting. The fact the your mid range is too rich, to me suggests that your low speed screw setting is not properly set. I'm assuming that you've already determined the high speed needle setting. Have you gone through the process of leaning the low speed mixture screw? I'd start from the nominal factory setting and start leaning 1/8 of a turn in sequence. Do a snap throttle advance to note the speed pickup and if the mid range is too rich, repeat the process again.

BTW I'm also assuming that your fuel tank is vented to the outside and it's not being pressurized via the exhaust.

Reply to
mn

A technique I worked out to get the proper pump pressure is to set the pump so that you could only get the engine to just four-stroke no matter how far open you set the main needle. This is the most pressure you need to run and any more can cause the midrange problems described.

One way to reduce the pump pressure is to lengthen the tube from the crankcase to the pump. Another is to install a restrictor in the same line.

Reply to
Paul McIntosh

I'll try those ideas out before I shell out more cash for a Perry carb. Thanks.

Reply to
Frank Costa

All of your assumptions are correct. However, I did set the low end to a point where any leaner and the engine cuts out pretty quick. I notice that the low end with the pump connected becomes very sensitive, because any richer and the engine slowly loads up and cuts out. I also HAVE to run an

11" prop to maintain a good idle. A 10" prop, and I just couldn't dial in a good idle below 3000rpm no matter what.
Reply to
Frank Costa

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