Thanks Frank. I hope so too

Doc,
I swapped coils and checked plugs, did compression test, trouble-shot the ignition system (replaced pickup coil),etc. It seems that everything I do helps some, but there is a definite leak that wakes up when the engine heats up -- (that may be a tell-tale sign). I put on larger *O* rings and make sure I tightened everything down evenly and fully. I tried to fully tighten the rear cylinder first and then the front. I don't want to over-tighten and strip out my threads.

Unless there's a way for air to enter above the manifold, it is definitely the flange leaking. It gives one "H E double toothpicks" of a vibration at about 60 and above, not to mention the distinct popping exhaust sound from the rear exhaust pipe.

In reading from the Mikuni website, I found out that the leaner air can produce a detonation problem. I think I have it. I just want to be sure that a new manifold will cure this UNLESS there's another way to install the one I have. I don't want to spend $$ on things that won't help me solve this.

I wanna ride my scoot!! ....

Rayjay