Changing BS34 to BS38 carbs

[Jiles]

I have a set of BS38s off a 1976 xs650 and have rebuilt them. I plan to replace the BS34 on my 1981 xs650 Special.
I know I will have to change intake manifolds and would like to know what else I will need in addition.
Any help would be appreciated.

 

[Jiles]

I have a set of BS38s off a 1976 xs650 and have rebuilt them. I plan to replace the BS34 on my 1981 xs650 Special.
I know I will have to change intake manifolds and would like to know what else I will need in addition.
Any help would be appreciated.

What year BS38 intake manifolds had vacuum pipe for petcock?

 

[member28833]

78 & 79. That series BS38 had no float bowl overflow pipe.

 

[5twins]

The BS38s run a fuel line to each carb. If you still plan to use the '81 single petcock tank, you'll need a "T" fitting to split the fuel line to feed both carbs.

 

[Jiles]

The BS38s run a fuel line to each carb. If you still plan to use the '81 single petcock tank, you'll need a "T" fitting to split the fuel line to feed both carbs.

My 81, with BS34 and single petcock, has a split single fuel line feeding both BS34.
Is there any reason I can't just use that?

 

[lakeview]

Won't transfer to BS38.

 

[5twins]

The "T" on the BS34 carbs is pinched in place between them. You'd have to pull them off their mount brackets to get it out. Then, if you ever wanted to put it back in, getting it to seal again may be an issue. I'd just buy a little "T" fitting to use.

 

[XSLeo]

Will the BS34 air boxes work with the BS38 carbs?
When you use the UNI-Filter foam pods you use different sizes where they mount to carbs.
Don't recall what size goes with which carb.
Leo

 

[gggGary]

The BS38s run a fuel line to each carb. If you still plan to use the '81 single petcock tank, you'll need a "T" fitting to split the fuel line to feed both carbs.

OR just cap one of the BS38 feed nipples, one feed keeps both carbs filled with the cross over tube. I only turn on the left petcock on my BS38 bikes.