Thread: OS91 Pumped Engine Tuning

Had a sod of a time tuning it earlier today. It's close but not right.

Now I'm not ready to give up with the pump just yet. I ended up today with the low needle about 10 degrees leaner than factory settings. Mid and high needles at just about 1.5 turns.

Its reasonable at high speed but bouncing on the pipe in idle. Picks up great on spool up but hangs on throttle down. Seems really hard to find the sweet spot so any advice or just give up and remove the pump ?

on the pump itself there is a screw on it which effects the flow. i have always had to tweak that on my 91's back in the day. open it up a small amount (1/8th) and hopefully will fix your lean low/mid.

cheers

That's lean on the bottom end ( idle ) I had a 91 HZ-ps it ran very well but , it used to spit out loads of fuel and I mean a huge puddle when starting and flood real easy !!
Sorry to say I copped out and gave up and removed the pump, it ran perfectly without the pump.

If you want one I have a brand new pump taken off a 91 you can try.
X rach

Thanks Rachel, the pump is less than 10 flights old, seems perfect. I was going to richen the low a bit.

Was yours around factory settings on the low?

Originally Posted by Mslater

Thanks Rachel, the pump is less than 10 flights old, seems perfect. I was going to richen the low a bit.

Was yours around factory settings on the low?

Yes I had to lean it off slightly but I never got the pump to run 100% , flying was fine just starting it without it flooding was pants !