ORIGINAL: qlacombe
I recently purchased a bobcat from an individual that had a GMS 76 engine with a 14X7 master airscrew 3-blade prop cut down to 11X7. Once in the air, in abougt 2 minutes it lost power and quit evidently from overheating. On the ground It would then overheat within a minute. carburator adjustment did not help. I replaced the engine with a Magnum 91XLS that I had used on a previous plane with no problems. I cut down a 3-blade 14X7 to 13X7. Everything seemed fine until like previously, after a couple minutes in the air, lost power and rpms evidently overheating. I am using 15% fuel that I was using on the engine when it was on the other plane. Very strange. I will try 30% next flight. I also had problems getting the nose to rise on takeoff. CG seems fine once in the air. I will add some height to the front wheel to add some lift from underneath . Question is, how much do I add? 1 inch, 1 1/2 inch, 2 inch? Anybody have any experience with this. I don't see many references to the overheating problems and I am suprised considering I am 2 for 2 for engine overheating. No other plane I have ever had has had this problem. Any other ideas other than the fuel? Thanks in advance for any advice you can give me. Quentin
Gl,
You should try 5%. You're overheating your engine. And with your current setup using higher nitro will cause more damage to your engine. You may also try shimming up your head with the 15%, your air in LA might high in humidity as well. On the ground you're engine won't unload as it does in the air. How's your pipe pressure setup, it may also cause a lean run.