Would someone please tell me how this darn thing works......

I have one without instructions......Was using it on OS 108 which was working great......But now find that nose up....the engine dies
and no amount of needle twisting has any effect.....

Pump has in/out at the bottom with a hex screw......Top has a nipple which I assumed was connected to muffler pressure to operate pump.......Spent 2 hours at the feild today messing with this engine............After reading old threads in this forum ,,I am to understand that the hex head on bottom actually controls maybe the flow ????

Carb on this engine is a 7D......

Thanks

Doesn't run on muffler pressure. Runs on crankcase pulses. You'll have to tap the crankcase with a fitting.

First, I don't understand how it was working great if it was rigged incorrectly? The single fitting on the end goes to a tap in the crankcase. I've attached a zip file that may help. I made a cheat sheet awhile ago on the pump. Check it out and let me know_bob

If you ran on muffler pressure, chances are that it got very dirty with oil residue, which wasn't there in the begining.

Crankcase pressure "ONLY" and line must not be more then 4" long. Use a hard neoprene like line. No need to pressure fuel tank, just vent to atmosphere. The hex screw is the flow rate screw. Turn it in and it increases the flow, out it decreases. There are arrows on the pump indicating inlet and outlet This pump generally works best with a Perry carb designed for the pump. Experiment with your carb and see if you can get the mid range to not run too rich. If you remove the pressure hex screw be carefull not to lose the small spring or to distort it by stretching it or twisting it. Turn the hex screw it until the top end goes rich, adjust top end needle till just peaked then adjust your low end needle till you get a smooth idle that will not bog(load up) after about 30 seconds of idle. If it speeds up and dies its to lean and if it slowsdown and dies or burbles its to rich on the low end. Once set they provide a very reliable fuel draw.