Opinions on GMS and Magnum engines?

any one know what the idle vavle is suposed to be set at on the gms .6

from the factor

-- jmys

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The factory setting plain doesn't matter - it is never optimal. After adjusting the HS needle to max rpm, back it off toward the rich side until rpm drops by about 3-500 rpm. Then adjust the idle needle for the lowest reliable (engine keeps running without stuttering). Rotate the nose down, and rpm should drop due to enrichment of the mixture cause by increased gravity feed of fuel. Tip it nose up and rpm should increase because the fuel mixture is leaned. When you have arrived at the point, check acceleration. You may have to adjust the idle a bit leaner or richer from best (lowest reliable) idle to get a smooth acceleration without stumbling. There is some interaction between the LS and HS needles, so to get the best overall performance, reset the HS needle after any significant change to the idle setting. It is an iterative process, but once set up right and the engine is well broken in, you will rarely have to adjust it.

BTW, these engines have a relativly high compression ratio and a large carb venturi. In my experience, they run best on low nitro (5%) fuel. After well broken in you can try higher nitro content if you feel the need for more power, possibly requiring an additional head shim (gasket) to lower compression ratio and/or a cooler glo plug (e.g. McCoy 59) to prevent pre-ignition.

Paul Mc has experience as a dealer of these and/or other engines from the same factory and may have additional suggestions, now that he knows which one you have.

Abel

Abel is right. You'll just have to open it a bit and give it a shot. The only way to learn how to do it, is to do it. Fortunately, you won't hurt anything if you are wrong. You can't burn up an engine by running the low speed too lean.

Ed Cregger

Thanks for the help. Its just like you said just keep adjusting it a little at a time till its right were you want it. It seems to run pretty good now I ordered some new glow plugs it some times dies after i remove the glow starter so ill try some new plugs to see if that helps. Some one told me they dont come with the greatest glow plugs so maybe its just a bad plug. Its seems to have good power im putting it in a great planes matt chapman cap 580. I think it will run good in it.

Our glow engines will never attain 100% reliability, but they can come close enough that we can enjoy them. Learning to recognize a glow plug that is unsuited for a particular engine, or one that has consumed its life span, takes a little time and experimentation.

Most new pilots aren't taught to plan ahead in case of an engine flame out. That is a shame. You can bet that full size aircraft pilots are taught to cope safely with such happenings. Model pilots should be too.

Keep a small notebook of your adjustments/experiments. You will be surprised at how just the act of writing something down will reinforce your memory of the experience. Being able to correlate previous experiences is what usually passes for being brainy in our society. It actually becomes fun after a while and it gives you something to talk about with other R/Cers.

Good luck and let us know how you are doing from time to time.

Ed Cregger