xs400 vacuum petcock

[pbaszxs400]

new to the forum, and read some posts on the xs400.

I just picked up and 81 from a barn (litterally) and going throught the tear down/ rebuild.

For rebuilding and tuning ease, can I run a separate fuel tank (i.e. lawnmower tank on handlebars) without hooking up the vacuum line on the right hand carb? Do I need to cap the vacuum line that ran from the carb to the tank when doing this?

used to working on old cb500 carbs....got to admit, these seem a bit foreign to me. The cb's throttle cable actually moved the slide up and down, I'm guessing these slide up based on vacuum?

I have all the goodies to get this right (manual, vaccum gauges, dwell meters, etc)

Thanks

[drewpy]

new to the forum, and read some posts on the xs400.

I just picked up and 81 from a barn (litterally) and going throught the tear down/ rebuild.

For rebuilding and tuning ease, can I run a separate fuel tank (i.e. lawnmower tank on handlebars) without hooking up the vacuum line on the right hand carb? Do I need to cap the vacuum line that ran from the carb to the tank when doing this?

used to working on old cb500 carbs....got to admit, these seem a bit foreign to me. The cb's throttle cable actually moved the slide up and down, I'm guessing these slide up based on vacuum?

I have all the goodies to get this right (manual, vaccum gauges, dwell meters, etc)

Thanks

you need to cap the inlet stubs as it will draw too much air.

these use mikuni Constant Velocity carbs, which use diaphrams to raise or lower the main needle via the engine induction which gives a smoother response. the throttle cable merely opens a butterfly valve in the carb.

you use the stubs on the rubber inlets to balance the carbs