ARE YOU TOO LEAN?
Tip Provided by John Greenshields - Magnum
Service Department
Running the idle mixture too lean can be damaging to the life of any engine, including Magnum. Many times,
pilots over-lean the idle mixture to compensate for other conditions that can cause poor acceleration. So, is your idle mixture
too lean? Here’s an easy way to check:
Once your engine in broken in and you feel the engine is running properly, use a tachometer to read the
high-end r.p.m.. Now, shut down the engine and richen the idle mixture exactly ½ turn (this way you know exactly where you
started from). Start the engine again and re-tune the high-end. Measure the top r.p.m. of the engine. Did it increase? If
so, your idle mixture is too lean. The idle mixture needle is actually limiting your engine’s overall fuel flow.
If this is the case, usually, a slight re-tuning of the high end and low end needle (but not so lean this
time!) will solve the problem. If acceleration does not improve without over-leaning the low end needle, you may need to check
your glow plug, high speed needle o-ring, and possibly your fuel for deterioration.
Look for more Tips from the Technician, only at HobbyPeople.net
John’s interest in modeling and full scale aviation began in the early 1940’s. John’s
passion for aircraft brought him to the airport before he was even old enough to fly and on his 16th birthday,
he qualified for his private pilot’s license before he even had his automobile license. John’s career in the hobby
industry began before Hobby People was started and when Hobby People (then Hobby Shack) opened in 1972, John was the first
and only employee. He has since retired and now acts as a consultant to our product development team. John is also our lead
Magnum mechanic. You can find John R/C flying regularly in the high-deserts of Southern California.
