ORIGINAL: Rcpilet

I think your a bit low on exit air. Put a lip on that hole in the back where the exhaust tubes exit. Maybe this will create a vacuum and pull more air through?

Carb:
http://www.davesmotors.com/store/product923.html

$69 [X(]

I used to find them on Sears parts site for $25, but their parts lookup is so frustrating--it's enough to make a guy want to run nails up under his toenails. [:@] Can't find them now.