engine roughness

[337G]

I have a 1976 337G and I am experienceing rough running on the front engine especialy after a cold start. If I do not give it a shot of prime it will stall or the other thing I do is keep it up at around 1500 rpm. It smoothes out after the engine is warm and will then idle at 1000 rpm but still with a bit of roughness. After flying and I shut down for a short while and go and re-start the engine it again runs very rough and then smooths out some what after getting up to normal temps. I have been told that this is normal but I dont agree. Any one else have this same experience?

Craig B.