GMS .40 Problem - RCCanada - Canada Radio Controlled Hobby Forum
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Old 05-15-2010, 07:00 PM   #1
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I am: Cliff S
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GMS .40 Problem

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I took the Enya carb off and reinstalled the stock carb. I did the mod that AJC talked about "Drilling the fuel inlet so the brass insert does not partly cover the hole.". It does not have an air leak cause I can throttle it right down to a nice idle, then kill the engine with low throttle.
The problem is when I go to high speed, I adjust the mixture from rich just barely too lean and do not touch the needle valve over a period of several seconds the engine will gain several thousand RPM's like some one leaned it right out. It is like the old tuned pipe engines of the 60's. Everybody I talked to in our club that has one of these problem engines has quit using it. Has anyone cured one of these engines?

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Old 05-15-2010, 07:55 PM   #2
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Re: GMS .40 Problem

I found the GMS 47 several of us run a bit of a bear until broken in. Motor would require gobbing rich on the ground to ensure any amount of power in flight. Even then it would quit at approx 1/2 tank. I had such a problem with dead sticks I ended up pulling the tank and replacing the rubber stopper and all the lines. Still did not solve the issue.

As for mixture, your behavior is indicative of how they seem to react until you put a few tanks through them. My previously described behavior went away after that.

However, tank height relative to the carb is also important, as is checking to see if there is the baffle in the muffler. Without it you could be lacking pulse pressure to the tank under high draw conditions.

You don't specify if you are running the remote needle and it remained with the motor during the carb swap, so if the problem is identical with either carb look elsewhere. Another possibility is the O-Ring on the needle valve.

A last recommendation is your glow plug. I found the OS #8 best in warm weather, while the #3 was required if I wanted the motor to keep running in colder weather. Your mixture settings may be a result of that.

p.s. My friends retained their stock carbs while I went OS with a remote needle. Regardless of any work we did, never could get the motors to quit, even with the barrel completely closed.
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