Miss fire in rear jug part 2.?

I'll try a compression test, but I did take the rockers off to replace the gaskets last year. didn't find anything wrong with the lifters or rockers. Didn't take the head off, to look at the valves. I'm not sure but, I will have to replace the battery. Bike would not start yesterday, in the cold. Last year the bike ran good in the cold. But this year it doesn't like the cold at all. ( below 50f.) Seems to run fine, with the choke pulled out. Once I push it in just a little, the motor will sneeze. As I take off, from a stop. Also it will sneeze when just running at about 50mph every once and awhile. ( Note: If I pull the plug wire, for the rear jug at idle. The motor stays the same. If I pull the wire to the front jug, it slowly dies.) I put a new coil on it this spring, and it has one carb. I also sprayed the intake with eather. You also can't change the timeing. Six years ago I had a new cam shaft put in, to lower the torke range. I used to tow a trailer behind, for camping with my wife. The cam shaft caused it to back fire abit more. But not to much more, than it did before. I guess I'll have to pull the motor out and rebuild it this winter. It's been six years and over 60,000 miles since that last time, so it's do.