thatscold

I am in the process of breaking in my force 21 engine on my Rex-x, and having run a few tanks of nitro through as per instructions I decided to check the glow plug. In the process I noticed a brown ring on the top of the piston head, is this normal? Or have I cooked the engine? Any help would be appreciated as a newbie I'd hate to think I'd knackerd my engine already![&o]

RaZ_Tx

i think the brown ring is from having the engine so rich its just a varnish from the extra oil its getting during break in wich is normal finish the break in process the brown ring should go away

thatscold

Thanks for your help, nice to know I haven't done any damage yet!