I own a 1983 Yamaha 650 maxim. I got the bike with no exhaust, so I installed headers. Also I replaced the factory air box with regular filters, 1 per carb. Now the bike runs so lean it pops through the exhaust, and runs hot. The bike has the factory main jet size of 110, what size should I be using??

That my friend is a matter for you to work out by trail and error! Don't assume because its poping its too lean! It might be drawing air into the pipe and igniting unburnt fuel (over rich mixture). Taking the silencers off often makes the mixture very rich.

Fitting pod filters might not effect the mixture untill wide throttle opennings as the air box should be able to supply 100% flow upto at least 3/4 throttle. There again it might send the mixture totally scatty. Hours of fun!