A few days ago I wanted to start with braking-in my LRP truggy engine. But it didn't went smooth.. at all... I couldn't start the engine. The pistion was stuck at the top. The flywheel just stopped at the top and the rubber flywheel of my starterbox just continues with spinning. You can see fine rubber on the chassis that is scraped off. I managed to start the engine 2 times though. The first day it started after many times trying and stopped after 2 sec. and the second day it started but when I removed the glowplug ignitor it stopped...
I tried al the tricks.

- pre-heating the engine (~ 150 fahrenheit, or 65 Celsius, this was the max temp I can get with a hairblower)
- loosening the glowplug a bit
- turned the fleewheel so it has a run-up
- Let the starterbox spin for a couple of seconds before pushing the car down, so it reaches max rpm

The starterbox is not the problem, cuz it's powerful enough as you can read. (it's the Ofna starterbox btw)
2nd Question: Do you think my engine is already damaged after al these (failed) attempts? Cuz it gets jammed with some force to the top ,but most of the time it just won't turn further... Thanks, appreciate all the help

Did you make sure that there is fuel to the carb? Unplug it at the pipe and blow on it and make sure you see fuel travel through your lines and to the carb. Double check that the glow plug is good and that your igniter is fully charged and that the piston is at bottom before you try to start it. Take your filter off and check that you have 1-1.5mm gap in your carb at neutral...you can also get another person to give it some throttle while you're trying to start it. You might want to also double check that the needles are at "factory settings" and maybe lean it out a tad since factory is usually super rich. Good luck

Yes I primed the engine etc., but that's not the problem. The engine just doesn't turn smooth, cuz it hasn't been run in yet.