1989 1340 panhead convertion won't idle without poping and when slowing down it backfires going up the gears is't strong and sounds good, any ideas???

 

Start with the simple stuff:

What do the plugs look like color wise?
Is the ignition timing set properly?
Is the carb clean and properly adjusted?

Oh and what is your 1989 conversion? High compression heads? Cam?

 

it has 4 plugs two I can't get out without taking the pushrods off but the other two look good. I don't know what the compression is and other than the stater and reg no one has touched it so I don't think the timing is off it does run strong going up hill and on the flat.

 

Sounds really lean.