What causes pops and bangs when cold

[Concrete-crusher]

Hi I recently balanced my twin webers and did a colortune and all seemed fine.

Next time I started up the engine pops and bangs until it's warmed up then again it seems fine.

Any suggestions as to where I should look first as the cause.

Steve S4

[billwill]

I think that is pretty normal behaviour for a twin cam.

Probably caused by the rich initial mixture that you get by dabbing the accelerator before starting. This squirts neat fuel into the inlets, some may get carried through unburned to the exhaust, so a short while later when hot exhaust gasses encounter it they ignite it and you get a pop or bang.

Go a bit easier on the initial dabbing.

[oldchieft]

I think popping back in the carb is lean mix, could be nothing wrong.

You have made too good a job in your set up and need a touch of choke when cold.

Jon the Chief