Right then, my 1994 FLHTC Ultra starts with a BANG when hot...

As soon as I hit the startbutton a loud bang from the exhaust (like a shotgun) and it fires up.

Doesn't do it all the time but now and then...not sure why?

It runs a 2-in-1 Supertrapp, Dyna 2000 ignition, S&S Super E carb, rest of the spec is unknown...

I've set up the carb as per S&S guide and it runs fine.

Another things I've noticed is that the revcounter seems to be off...when it displays around 600 rpm seems more like 900 rpm and if I set it to idle at 900 rpm per revcounter it idles way too fast!

Could this be caused by the Dyna install?

 

Something that helps is to just bump the start button to barley turn the engine, it will release the built up compression. then start it.