Here's a few ideas...
Had the tank off? Is the vent line pinched? When the problem occurs open the gas cap and if you here a "whooosh", well, there ya go.
Are the carb rubbers seated correctly, pliable, and the clamps tightened securely?
Are the little squirrel condoms on the 4 vacuum ports on the intake in good shape and stuck on there securely?
And finally, on a post about dialectric grease a short time ago, someone mentioned to use it sparingly, if at all, on the high voltage connections, i.e. coils and plugs. Maybe you over-gooped those....... a "film" should be sufficient on those....
I'm sure there will be other opinions coming any time now, so stay tuned.....
