Can a big bore exhaust cause exhaust popping

Have rebuilt my ST70. The engine had not run for many years but seemed very tidy with nil bore wear etc. I am having trouble getting the bike to run sweet.
Everthing electrically is new,Points, plug, condenser, coil etc and i have the timing bang on the mark. It starts sometimes and just seems erratic. I fitted a new carb rebuilt kit, still bad, so fitted new carb, still not running well. Often as I try to kick start it it pops and back fires. I am now wondering if the big bore stainless steel exhaust pipe and muffler installed can cause this. Has anyone fitted an exhaust like this? any problems??

Sorted my Exhaust popping problem. When I assembled the engine I did not have a 1/4 drive torque wrench so tightened head stud nuts by feel and suspect i was under torque so probably had a small leak between cylinder and crankcase or between cylinder and head. I purchased a small torque wrench and re-assembled it all with new gaskets and torqued up to the 7ftlbs. Bingo! No more popping on startup and shes running very sweet. The big bore exhaust did not cause the popping.