Recently I have been reading of some folks advocating the high needle be set at max rpm for flying, and not at a slightly richened position as I am accustomed to do.

As my style of flying does not require every last rev from my engine, I will continue to lessen max revs by 200 rpm for flying. However I would really like to know if my way is the preferred way or if there is a new line of thinking about this.

Karol

I would never set the needle to max and leave it, I can almost guarantee that this type of tuning will end in a lean run and a dead stick
Derf

I don't use a tach to set my gassers. It's all by ear...... Set the low for good idle and transition, and rich enough where it won't lean out in a harrier or rolling harrier. I set the high speed to where I can TR for a minute or so, then go full throttle straight up till I can't hardly see it anymore. If it doesn't lean out, you're ok. Also if you plane is propped right, do some full throttle horizontal runs and let it wind up and unload, land, and pull the plug. As long as the plug is tan and not white, you're good to go...... If it's white, you're too lean and need to richen the hs needle a bit.

If you're talking about glow engines, use the pinch test. At full throttle, briefly pinch the fuel line. if the engine sags immediately, it's too lean. If it speeds up a little but keeps running, it's just about right.

Dr.1

A gas engine is not at all like a glow engine, and different rules apply. Once you [link=http://www.prme.nl/forum/viewtopic.php?t=10]have the carb set about right[/link], and for safety that is the rich side, you go by plug colour readings alone, not rpm.
The plugs tell the story concerning plug heat range, fuel jetting and ignition timing, depending on what part of the plug you examine.
Want to know more? Google for plug reading, and you'll find a wealth of information.

Using your very well written and informative piece on " Tuning the Walbro ", I tuned the carb on my G23., and after a brief WOT run, the plug was inspected and looked as it should.

However in the final tuning steps of your article, you mentioned richening the high end by opening the high speed needle 1/16 turn. What does this approximate to in rpm loss....just a guesstimate.

Karol

on my MVVS 35cc gasser with a Zinger 20x8 Pro (for flight) I tune 200 RPMs under peak RPMs, after a couple flights I checked the plug and it was glossy black, but the motor has only 2 gallons burned threw it and it doesn't sound rich as it flies at full throttle so I will leave it at that..

Jim

probably no, or very little rpm loss. This rpm loss thing stems from glow engines who need it for cooling, and is an inferior measure to go by for gas engines. Final adjustments by plug readings is best.
Gas engines provide best power at a rich setting. Richening up still further into power loss is not the way to go, except for idle.