Two different models, right one?

[benjo]

Hi All,

So I have ended with the craziest carb configuration for my 1981 gs450. I have the twin carbs with 45 pilots and 115 mains, and in the airpods I have put a penny washer with two holes drilled through it. Absolute maddness. Things brings me back to a question I posted on here a while back.

There appears to be two different models of the Mikuni BS34ss carbs.
One like this: https://images.cmsnl.com/img/partsli...ig-12_fb86.gif

and one like this: https://images.cmsnl.com/img/partsli...ig-12_3696.gif

The first one has the jets sitting in the bowl where the second one has the jets sitting in the body. I have the second sent of carbs. I took them off a GS750 which have a quad-rack of 34s. I took carb 1 and 4 and put them together to make a twin set. (It's tough finding parts in South Africa)

So questions:

1) Do these different carb types affect performance? even though the are both 34mm?
2) You measure the size of the carbs by measuring the diameter of the inside of the carb that goes to the engine side, right?
3) Do I have the wrong carbs for these things?!?!?!?

[Steve]

Yes, there were two types of carbs on the 450s. Not sure if the change was in '82 or '83. Your '81 likely came with the ones in your first link.

1. With proper jetting, there should be no differences.
2. You are correct with your measurements.
3. You have different carbs, not necessarily wrong.

I have never heard of anyone using the outer carbs from a four-cylinder bike on a twin. Not sure how that would work, as there is no place to connect the throttle cable, which is connected to carb #3.

.

[benjo]

I have never heard of anyone using the outer carbs from a four-cylinder bike on a twin. Not sure how that would work, as there is no place to connect the throttle cable, which is connected to carb #3.

.

See this link to this pic: http://www.motorcycles123.com/mc123_...i_carbs_lg.jpg

It's pretty straightforward,I took the middle mechanism on the butterfly spring between 2 and 3 and moved it between 1 and 4. Pretty straightforward.