Fairy recent carb rebuild. New spark wires. Running pretty decent.

Hen the other day it started to randomly lose power and backfire out he exhaust like it's getting too much fuel. Eventually it would start up but wouldn't run well enough to get anywhere.

Replaced the coil. No dice.


Ideas?

 

There could be several reasons for the poor performance.
The list might include;
Backfire could come from
defective distributor cap, plug wires incorrectly placed , need to be kept separated,
lean mixture that could be the result of incorrect float level in carb which could be caused by float needle valve that was not designed for unleaded fuel (swelled),
Incorrect timing etc.
I'm pretty sure there could be more reasons, but those are just some of them.