Drivetrain, unless it's binding for some reason won't usually cause
that kind of problem, but a retarded timing setting will. Make sure
you're at 10 degrees Before Top Dead Center (BTDC) with the vacuum
advance line plugged on the distributor end. Ten degrees will work with
most lower grade fuels.

If that is good, then look at your accelerator pump settings ( I prefer
the longest stroke, especially in cold climes in winter) and make sure
it's squirting into the carburetor throats.

Could your exhaust be bent from a rough road, high centering or backing
into a dirt pile?

Budd