Is it possible to adjust a carb using a vaccume gauge? I have heard that a carb is at peak performance when the vaccume reading is at its highest.

 

which carb to you have?

the intake track is very short on a HD, so this is not a reliable way.

wide band 02 in the pipe is the best way, on a dyno you will be able to see your changes.

a good resource is the Mikuni tuning guide.

you can dial one in a day or two.

 

Its a Keihin 40mm cv on a 2005 Roadking

 

Vacuum gauges are usually used to synchronize the carburetors on a multi carb engine.
I had a dyno tune done on a carbureted BMW once and it worked great - saved a lot of screwing around.

 

A vacuum gauge is useful for tuning mult-carb bikes, but I don't see it being much use on a single carb bike. There doesn't seem to be an easy way to tune a carb except with a lot of experience! The book will help, but a novice may not find it easy in practice. That is why top tuners in the past were worth their weight in gold. These days we have machines in the form of dynos that make the job easier and quicker. Having seen my own bike set up on one I would recommend the experience.

 

46-48 pilot, 175-180 main, air idle 3 turns out.
Good starting point.
Scott

 

Dude you're getting too cosmic with this. There's only one carb so all you need to do is get it close to optimal AFR's for the style of riding that YOU do. Find a good tuner that will do a few AFR runs for you without screwing you around with all those high rpm hype numbers. Trying to screw around with vaccum readings will only result in a hacked up cv40 and you'll just be buying another slide to replace when your dremel has chopped up this one. If you ride for the enjoyment of riding you can get these things pretty dam close in your garage. If you buy into the high rpm dyno crap you'll be chasing your tail. Tuning depends on what type of riding YOU do, so take all the forum suggestions about tuning with a grain of salt.

 

You're the only one who's talking about "high rpm dyno crap".

 

Oh,OK.