I bought this bike a couple weeks ago. I was told the carbs were recently cleaned and synched. The bike sounds like it backfires/or misses though when it heats up some, 2-3min of running. The person I bought it from had the spark plugs changed also, and said that was when the missing started, the wires were not changed and he was told that, or the coils were more than likely the problem.

Is there a way for me to test and see what the problem may be? I tried to see if I could see any sparks or anything in the dark but saw nothing, and the wires look to be hardwired into the coil.

Also the bike seems to run much better if I leave the choke all the way on, don't know if that helps any. thanks  

The choke being on just makes for a richer mixture,Could be your valves need a adjustment and if your bike uses a point system they might need to be adjusted.The best bet is take it in to your local motorcycle shop have them check it out.My 1977 XS 650 did that until I changed the points but every bike is different.