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Old 01-01-2005 | 07:37 PM
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Flyer Freq
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From: Appleton, WI
Default RE: GMS Engine Tuning Problem

O.K. Guy's!

We had our annual Frozen Finger Funfly today, and my friend finally turned his .47 over to me. The first thing I noticed was that his carburator has two O-rings sealing it, where it mounts to the crankcase, and my old .47, which runs perfectly, has only one. I would say that he should have a better seal around the base of the carb than mine does, but the O-ring is really stiff and hard. I can't help feel that changing to a silicone O-ring would help here. I will try to get another O-ring, as I am afraid I knicked the O-ring while removing it.

I next removed the inlet nipple. About 1/3rd of the hole in the brass insert was covered by the edge of the carb body. When I compared it to mine, the edge of the hole in the brass insert was lined up with the edge of the hole in the carb body. The newer carb appears to be consistant with the findings you have made with the bad runners. I took the rest of the parts off the boddy and laid the carb on its side and knocked the insert out with a rubber hammer. It came out with a couple firm taps. The hole in the insert was uniformly round on one side of the barrel, but the other side resembled the shape of a kidney. I can't be sure which side was facing the nipple. When I compared the holes in the brass insert from my good carb, the holes in mine were nice and uniform on both sides.

Everything else between the two carbs looked identical. At this point, I reassembled the newer carb, being careful to line up the holes. I used a nipple from an air tool to slide over the end of the brass insert. I then pounded the insert into place. I made sure I didn't pound it in too far. I wasn't sure if installing the high speed needle barrel would pull the holes out of alignment when tightened down, but it did not. The barrel is tight and everything is in proper alignment. All that remains now is to run the engine with a new base O-ring. I wish I didn't have to change the O-ring, as now I won't know if the engine runs well, if it was the alignment of the holes, the new O-ring or both.

I will see how quickly I can get a new O-ring, and report back. Engines don't run particularly well in the severe cold we get here, but I should be able to tell something. I may try putting the newer carb on my engine to see how it does. After all, my .47 doesn't have that O-ring inside the crankcase.

Till later!!!

Andy