Dave,

I seems to be having a problem with my YS 63 at high rpm. If I run the engine up to peak I start hearing a clanging that sounds somewhat like the valve train. I have pretty much though this was detenation. When i richen my top end to stop this I have to richen from peak about 700 rpm. My top rpm is 11500 and I have to richen to under 10800 to get this to stop. This is on 30% heli fuel. I have also tried 20% Pro Pattern with added Klotz Technoplate oil. Both times it would have this same problem at high rpm. I have had this engine for about 3 months and have not been able to get it to run reliably. It has had about 2 to 2 1/2 gallons of fuel through it. I am thinking I should send it in for service.