OK-- Let me say I really like OS engines. I am not new to either engines or the sport. I have / have had 40,46,61,108 OS's.

IMHO this 91 is a POS! Perhaps os compromised too much trying to compact the size! Let me be specific--it's the only engine I've heard preignition in--it nocks like hell!! Have blown out two glow plugs--yes I had Clarence Lee helicoil the head-- the head bolts are constantly loosening and I've tried 10% fuel to 20% fuel with negligable diference. The prop is a ProZinger 14/6

If any of you gear heads can help me out I'd appreciate it-This thing has a 51 year old man ready to cry!!!!!!