Yamaha Suzuki Carb xover

[Crazcnuk]

Hi there, short time viewer, first time poster!

I picked up an '80 Yamaha XS1100G, recently, and it has what appear to be Suzuki BS34SS carbs on it.

They have a part number of 49150 on the carbs.

The bike they came off of has been parted out, but I was trying these on an'80 XS1100SG, but, so far no luck. They've been cleaned and floats adjusted to 22.4mm (although that took a lot of tab bending!) as per the advice on this site.

The bike starts right up, idles fine, but any throttle and it will bog down and die.

In Yamaha terms this style of carb (with the plug over the pilot jets) would normally have:

137.5 mains, 42.5 pilots, 185 air jet, 5GZ6 needles and X-2 needle jets.

These have

115 mains, 40 pilots, 170 air jets, 5d50 needles and X-6 needle jets which I am told is stock for 80-81 GS1000s.

Just wondering if anyone knows if the BS34s had any other internal changes between the BS34II abd the BS34SS?

The Suzy carbs appear to be a half step between the 78-79 BS34 II, and the 80-81 BS34 III that the XS's used.

[Don-lo]

Do you have the yamaha airbox on there?

Is your vacuum advance working correctly?

[Crazcnuk]

I've tried it with and without the stock airbox.

The vacuum advance works correctly, although, at idle the suzy carbs rattle it more than the Yammy carbs do. The vacuum port on our carbs, that is in the same position on carb #2 is for our advance. We get vacuum for the petcocks off of the #2 carb manifold (boot).

[Don-lo]

I was talking about the vacuum advance under your ignition plate (points cover)

Absolutely, use the airbox. But realistically, these carbs may not exchange well.

What do the spark plugs look like?

[Crazcnuk]

So was I, what other vacuum advance would there be?

I did find out that Suzuki puts the needle springs on the opposite side to the Yamaha, so I corrected that and it helped a bit.

As far as straight running, the airbox should make no difference. That is more getting into the fine tuning.

Not sure why they wouldn't change over. The engines are almost identical. Similar cc's, hp, compression etc.

The thing that is odd is that the XS's basically came with 2 setups, and a couple of small variations. Suzukis seem to be jetted all over the place, even among the same general models, and while we go up a jet size or two for common mods, you guys like to jump 5 jet sizes at a time.

And what the heck is an air equalizer?