I made a previous post on how I was having problems with my Saito 91 4-stroke.
It was looseing RPM's after it had warmed up. Tried a new plug, checked out the plumbing, adjusted values, tried everything I could think of. My son said he would take a look at it and of course he found the problem.

The engine is mounted sideways so when it warmed up the choke slide vibrated down and slightly choked the engine thus loosing RPM's. I would of thought that with the engine being choked that it would run rough and smoke alot but it didn't.

Thanks to all who tried to help me.