Originally Posted by
flybyjohn
Thanks for all the help so far guys. What does it mean when the engine starts to surge? This happens when I am leaning out the needle valve and then the engine will surge ( rev die rev die ...) What should I do at this point? Do I increase the compression slightly, or just richen the needle a little? Is this the "Brrr Brrr Brrr" sound you were talking about in the other post Dave?
Once at operating temp, I would richen until the engine reaches peak, then decrease compression slightly. If RPM drops off, increase compression and check for an RPM increase. When you no longer get an increase in RPM, stop increasing compression. Lean the fuel mixture to check for further RPM increase. Back off just a little from peak. On a plane the prop will unload a bit so final adjustments will depend on how it performs in the air.
Of course these are full throttle adjustments. Low throttle depends on your carb.
George