ORIGINAL: crmamx
I don't believe it is the engine nor do the experienced flyers. It runs like a top on the low and high ends once started and no problem in flight. So it would have to be fire or fuel. We replaced the glow plug but that didn't help and the plug glows ok when removed from the engine and hooked to the glow starter. But I am going to try the OS #8 plug as recommended in a post.
If after priming the engine, you are cranking it a lot ( as you indicated ), and it otherwise runs good, once started, the problem is NOT in the engine nor it's tuning.
Don't change the plug. The engine is already running fine!
Use clear fuel tubing from the tank and watch what happens to the fuel after you prime the engine.
I suspect the fuel is running back into the tank.
Also do you bring the throttle to idle immediately after priming? This helps prevent the fuel from siphoning back into the tank.