I bought this engine when they first hit the streets, it ran flawless out of the box, idled reliably on PowerMaster ys20/20 and had the power greater than most .60 two strokes. I definately thought I would never buy a two stroke again as this little powerhouse weighed as little as a .46 and power of a .70. Well after about 3 gallons it just no longer wanted to transition smoothly, I only have 5 gals maybe through it total and it has become my least favorite engine on reliability issue. A am confident no leaks exist in tank and plumbing, and no debri is present in ports, timing was also checked with brass shim feeler gauge to .007. It seems to idle fine and full power fine it's just the lower center transistion thats a pain in the butt.

Where do I start, I am highly regarded at my home field as a 2-cycle engine guru but these YS are a horse of a differant color, Ive read the website and comprehend how it works, what am I missing to get that out of the box transition reliability back again.