Well guys I took the easy way out.
I added a 3rd exhaust pipe and it made the difference.

The 1st 2 pipes went about 3/4 the length of the muffler and were 45ed and faced the back wall.
The new pipe is as flush to the bottom of the muffler as I could get it.

It may not be developing top power but watch me rock back when I rev it up.
The thing falling off the other side of the fence is a metal sign.
It was blown off a large head screw that barely fit through the hole.
This should make a 15 pound plane jump into the air.
My biggest concern now is ground clearance for the prop.
It is easily turning a 22x10w prop, probally a 24x10w would drop the rpm a little.
But I'm going to need a 3-blade prop for ground clearance.
Anyone have experence with a 70 something cc engine and a multi blade prop?

Compair this video to the 1st one.
2nd Video: http://rcuvideos.com/item/GYZZ4BDXYD2G4VVP

1st Video: http://www.rcuvideos.com/item/BMV2KV388GZSF0NZ