I installed a Perry Pump on a Tower 46 because I was having problems with the engine getting too lean when vertical. The problem I'm having with the pump is that at full throttle it causes the engine to surge badly. It seems to improve when the engine is cold or if I increase the amount of fuel from the pump. Problem is, if I increase the fuel from the pump then the midrange is too richand the engine bogs down during transition from idle to full. Any one had this problem or have any suggestions?

I ran the engine static again without the pump and there is no surging so I'm sure it is pump related.

There's been some discussion off and on here about surging. I always thought it was because the engine was too lean. But an experienced friend says that the prop is too small and that there is not enough load on the engine.

Why don't you start it up again and try to adjust the pump where the mid range is about right, then try to richen up the HS needle some? These two will be inter related somewhat and you will have to go back and forth adjusting both until you get it right.

The Tower tends to be a little rich in the mid range anyway but you want to get it to where it doesn't quit on you.

Good luck,

Jim

I've always set the needles the same way as I do w/o a pump but, I have read to try setting the needle valve while throttle is somewhere in the midrange. I have also found the low end is set leaner than I would have guessed. Maybe you do need more flow from the pump and your transition could be improved by going leaner on the low end. Engines that are notoriously rich in the midrange is where the pump has helped me smooth it out.

Thanks, I'll try both ideas. I'll even try a bigger prop. running an 11-7 now. 12 is about as big as I can get on this plane tho.