Smooth Barrel

Sometimes the barrel of the carby can be rough from casting dags and this causes air resistance therefore not allowing as much fuel and air into the bore. This can be removed with an old chisel that you don't mind getting blunt, a dremel with a grinding disc or sandpaper.

First remove the carby from the engine to prevent any metal filings falling into the cylinders and then stuff a clean rag into the intake to stop dirt entering in. Gently remove the dags slowly and try not to scratch the barrel. If the barrel is round where the dags are then use a dremel or sandpaper as a chisel will only create more work later on.

If your carby is rough around the whole barrel then you should leave it as it is. It is there to atomize the fuel with the air to provide better combustion for more power.

You can also remove the casting dags in the intakes and exhaust ports but remove the intake and exhaust manifold so metal filing to not enter into the cylinders. Repeat the same process as you did with the carby but leave the roughness there as well.