Carb settings

My rule of thumb before setting carb adjustment is to do an old fashioned tune up, what used to be called "plugs and points". The object is to get spark as good as can be, timing set spot on, tappets set, air filter cleaned, etc. etc. Carb setting should be the last thing to set, never the first. This was the message from my fellow workshop mechanics when I was learning the trade and there turned out to be a lot of truth to it. Wise words indeed. Being young and brash I resisted of course..

I set the idle mixture with timing retarded and engine fully warmed after a 10 minute+ ride. Stop and immediately tune the idle mixture. Effectively find the midpoint between rich and lean. The main jet needs to be set by performance on the road. The engine should pull without misfiring from being too rich or lean.

Once I'm happy I've got these two settings close, I mark the positions of the two needles as in the pic.

Marks allow fine tuning, perhaps a click or two either way to see if there's any slight improvement. Marks also allow the original setting to be re-established (with accuracy) if need be. In addition this is handy if someone messes with your settings as some kind of sick practical joke.