Hi,

It was very cloudy with a few sunny breaks today and I had 5 flights with the GMS .47 today without the home made baffle(s).

The first flights two were used to fine tune and adjust the engine (with plenty of landings to tweek the needles) and the last 3 flights were great without adjusting the carb.

I'll go over what needs to be done. The problem seemed to be the fuel hole that is below the fuel input nipple in the carb, not lining up with the fuel nipple hole. I think this causes fuel starvation at full throttle.

What I did was to first carefully drill out the exhaust nipple and carb input nipples to the next size larger (to 5/64 of an inch). I then "free handed" carefully drilled the brass insert below the carb nipple to 5/64 inch (in the future I would drill the nipple, then install it, use it as a drill guide to carefully drill into the brass insert to avoid any damage to the carb's nipple threads). The new, larger holes now lined up and gave me better fuel draw and better "exhaust to tank" pressure. Be sure to remove any brass filings when you drill the carb. Note: Drilling the holes will modify the engine and therefore void your warrantee, so if you chose to do this, be very careful since its at your own risk.

At first I had a difficult time adjusting the engine high speed and low speed settings - these seemed to intereact with one another. Example, leaning the idle, also leaned the top end - I would readjust the top end, and it would affect the low end, and I ended up with a never ending cycle.

What worked for me was to:

1. First go to wide open throttle (WOT), adjust the high speed needle for max RPM then, while while still at WOT, tweek the low speed adjustment to fine tune the engine at WOT.

2. Then go back and adjust the high speed needle and then back again to tweek the low speed adjustment. Keep this up until you have the best WOT performance.

3. This will be very close to the proper adjustment at both WOT and idle.

4. After you get the best WOT with both high and low speed needles, carefully idle down and adjust your low speed RPM (by programming the transmitter or adjusting linkage).

5. Once you find the best idle speed for your prop, then "poke" full throttle. Turn the low speed adjustment no more that 1/4 turn either way until the acceleration from low speed to high speed is smooth. My low speed needle adjustment needed to 1/8 turn leaner (tightened "in" ) .

6. Test at WOT with plane level and nose up. Mine worked OK at this point.

The final adjustments for me were:
Turn in high speed needle in until it just stops, then back out 2 1/2 turns.
Turn the low speed needle in until it just stops, then back out 1 3/4 turns.
This may not be dead on for you, but will give you a good starting point.

I hope the above will help someone else make their GMS .47 the power house and reliable engine that it can be.

I hope someone else will give the above a try and let us know if it worked for them - this one test is not enough to verify if this is the "fix".

If you have any questions, or I can assist with anything, please let me know.

Fly4Fun,

Wayne Miller