It could be a number of things, but it does sound like your carb is running rich or the accelerator pump squirts too much fuel.
- Always best to rebuilt your own carb with a special kit, or check every part on a remanufactured one, before use.
It's hard to get a good remanufactured simple fuel pump these days, let alone a carburetor that was done right.
Definetly re-check the float level. - With modern fuel you want to decrease the recommended float adjustment by up to a 1/16" when setting it.
To lean out the mixture, you can try a smaller main jet in the Roch B. if everything else on the carb is good. The shop manual should list the correct size, in the specifications/carb section, if you know your carb is stock.
The leanest setting when timing is usually the best.
Keep advancing the timing in small steps until you hear a slight ping (screeching sound) when you accelerate on an incline in 3rd gear with wide open throat and stock transmission. Then retard back to no ping.
The popping sounds at deceleration comes from unburnt gas in the exhaust, from a too rich idle setting.
With just one carb and the stock exhaust system, you shouldn't get that sound.
I found the best idle setting to be the lowest idle speed that keeps the engine running without stalling after deceleration and shifting back to neutral.
That would be around or a little lower than 500rpm, just as the shop manual suggests.
