Hi,

I agree that in theory the baffles should not be needed, however I just got back from the flying field and have tried several things. The results are below.

First I'll re-state that this on the older style GMS, and all air leaks have been sealed, except for a very small amount of air escaping through the front bearing. Some state this is normal - I'm not sure. I should also let you know my newer GMS works great and so I have experince with both styles.

Today I tested without the baffles, and also with different number of baffles. In all cases I ran with a 12.25 X 3.75 prop.

I should let you know the older GMS works fine with the newer GMS muffler. So I have concluded the problem is with the muffler and the pressure feed. If you have any other suggestions to increase the pressure feed, I would appreciate them.

I reinstalled the older muffler and worked with it.

I first tested with the two baffles as shown in the previous picture, and all worked fine, adjustments were easy, idle was good and high speed was constant.

Second I tried smaller baffles, that is, 1 inch instead of 1.25 inch. This gave me a broader adjustment range at high speed, but I did get more RPM. The engine would quit after a while at full throttle for no particular reason.

Third I removed the baffles completely and again I got more RPM but the engine would quit running at full throttle after a while.

Fourth, I installed just the original first baffle (1.25 inch) at the front of the muffler. The muffler was a little louder, but all adjustments were easy to make. The difference in RPM was 200-400 less than without any baffles installed in the muffler.

I settled on just using one baffle, the one closest to the front of the muffler and flew the GMS with a Somethin' Extra for 6 flights with no problems.

I'm convinced the problem is with either the fuel draw, or low exhaust pressure to the tank. Whatever the reason, the baffle does the trick for me.

In this case I have a working, flying engine instead of sticking it on the shelf.

I appreciate everyone's input, however, if you haven't tried the above, and are commenting, I should let you know I would have agreed with everyone BEFORE I got this engine. If you have an old GMS .47 that isn't working, give it a try, I think you'll be surprised at the improvement. In one of the previous posts someone stated "you gotta do what you gotta do to make it right" - good advice.

If you have any other suggestions I can try, I will give them a shot, just let me know.

If you have one of the older GMS .47 with the same problems, I hope you will give the above a try and give us your feedback.

Thanks for your help,

Fly4Fun,

Wayne