[Roscoe]

Worksalot,
Just to give you an update, I took off both float bowls and metering blocks and sprayed them down with carb cleaner. Then blew out all the orfices, changed the accelerator pumps and the little diaphrams that go with them, took out the idle mixture screws, etc. I took off the fuel lines that run from the final filter to the carb and blew them out.

I took it out today and it runs fantastically well. Like a new car! Very responsive, no stumble or pipe backfireing. Looks like that was the problem.
Roscoe