The backfiring indicates it is running very lean. Pull the carb and ensure the jets and passages are clean. Also check the intake manifold for tears in the rubber... or missing O-ring seals on the manifold and carb. Most CBs are jetted lean from the factory. When you remove your carb to clean and inspect the jets... note down the jets installed. Post up here which ones you got and we can give recommendations.
Also check the A/F mix screw setting... shouldn't be screwed all the way in (tight).
Might also check you don't have an exhaust leak somewhere.
Cheers!
|