'75 KZ400 jetting up

Howdy! New to this forum (came from SVRider). I have a 1975 KZ400 with stock kei hin carbs and planning on doing straight pipes. I know it's hard finding any parts for these but is there any info on bumping up main jet sizes and needle settings?

I added an aftermarket better flowing exhaust to my 76 KZ400 when I was still running the stock carbs and going up a size on the main jets was all I really needed along with shimming the needle with a small washer or two. There are no grooves in the needle to change the settings, you'll need to find some small washers that will fit over the needle to lift it a little. Though you may not need to make any adjustments. Try it first, read the plugs, see how it runs and adjust from there.

FWIW I recommend not using straight pipes, some type of muffler would be better to provide some back pressure.

Are you aware of the fact that the bike will run poorly with straight pipes?

Take a look at the link below. Notice how much research, testing, measurement, money, expertise, etc. goes into engineering a decent exhaust system. Then consider the effect when one takes a hacksaw and lops off a chunk of it. Ed

www.epi-eng.com/piston_engine_technology...ystem_technology.htm