Getting a lot of popping and backfire...

I picked up a 1980 KZ440 LTD. It ran but it was sluggish, but there was no backfiring or popping, so I did some work on it like plugs, wires, valve adjustment, carb teardown and cleaning, new carb hoses and some inline filters, checked for air leaks around carb boots and air box. Everything seems to be well and it is running much stronger than before but I am now getting a lot of popping (from exhaust) and backfiring (from the carbs) at idle and while running at higher RPMs. It pops about every 4-5 seconds and will backfire about every 10-15 seconds. Compression in both cylinders is good (tested at about 120psi) and I set the valves and carb floats to factory specs. Plugs look brown when I pull them out, one had a bit of white on the tip but not too much. I am stumped and if anyone could tell me what to check or what I may have done to cause the backfiring I would be very grateful. I have heard a lot of people say it is running lean but I can not find a screw for the air fuel mix on the carb...

Jayblefty wrote: I picked up a 1980 KZ440 LTD. It ran but it was sluggish, but there was no backfiring or popping, so I did some work on it like plugs, wires, valve adjustment, carb teardown and cleaning, new carb hoses and some inline filters, checked for air leaks around carb boots and air box. Everything seems to be well and it is running much stronger than before but I am now getting a lot of popping (from exhaust) and backfiring (from the carbs) at idle and while running at higher RPMs. It pops about every 4-5 seconds and will backfire about every 10-15 seconds. Compression in both cylinders is good (tested at about 120psi) and I set the valves and carb floats to factory specs. Plugs look brown when I pull them out, one had a bit of white on the tip but not too much. I am stumped and if anyone could tell me what to check or what I may have done to cause the backfiring I would be very grateful. I have heard a lot of people say it is running lean but I can not find a screw for the air fuel mix on the carb...

Did you ever figure out the problem ? Having issues with backfire out of the carbs and little puff of smoke

Check your valve timing and your ignition timing thats all I can think of.