Posted this on the Gas Engines forum, and someone suggested I post it here on the Fuji forum, which at the time I didn't even know existed!

Bought a G.P. Giant Supersportster and a Fuji 32EI - first giant and first gasser. Engine ran fine right out of the box but started running rough after a few flights. I found that the screws that attach the diaphram cover plate to the carb, and the carb mounting screws were not very tight. Fixed that problem and the engine ran much better for a few flights and then turned to crap again. A whole lot of needle tweaking, carb screen cleaning, gasket inspection, etc. didn't help, so I removed the engine, tank, fuel lines, ei module, battery, and mounted them on test stand. That's where I discovered.....

PROBLEM #1: The screws that attaced the carb to the spacer block were too long! The screws extended all the way through the spacer block and bottomed out on the cylinder block. (As soon as I saw that, I remembered reading something about that on this forum.) I removed the carb and found that the spacer block was warped, probably because the carb mounting screws were trying to pull it away from the cylinder block while the spacer block mounting screws were holding it down. I honed all the mating surfaces flat and shortened the screws, put the carb back on the engine, and it ran smooth as silk. Hope is restored! I fine tuned the carb per info from this forum, mounted the engine back on the plane, and took it to the flying field. (From this point on I will voluntarily delete the expletives.) At the field, the engine wouldn't fire at all, no spark. Hopes dashed once again. The battery checked OK, so I took the plane home and tore the ignition module and battery (4.8 V, 1100mAh NiCd) out of the plane. After a little troubleshooting, I found ....

PROBLEM #2: The MPI switch harness that I used for the ignition battery was bad. (The switch harness is the one part that I didn't move to the test stand with the engine.) In the 'off' position it was OK, so the charge side of the circuit was fine, but the 'on' side of the switch was bad so I wasn't getting any juice to the ignition module. I've used these MPI harnessed before on receiver batteries and they have always worked fine. The EI module doesn't draw that much current, according the the specs anyway, so I'm thinking that engine vibration might have caused the failure since the switch is mounted up near the firewall. I replaced the MPI with a Cermark DSC harness that I read about on this forum on both the receiver and the ignition batteries. I took the plane to the field, where the engine idled, transitioned, and pulled the plane around just fine for the way I fly (2D). I'm hoping that the Cermark switch will hold up better than the MPI. Anyone have any thoughts on that?

Just an FYI, especially for the other newbie Fuji users out there.