Mikuni Bs34ss - Two Models?

[Guest]

Hi all! I am currently rebuilding a 1981 GS450s and have been having carb issues. What I have found is that there appear to be two different models of the Mikuni Bs34ss carb.

The twins I have look like this: https://lh4.googleusercontent.com/_z...2/P1040047.JPG

But I have seen other models like this: http://img.auctiva.com/imgdata/5/9/8...4103405_tp.jpg

You can see that the bowl shapes are different as the jets sit in the bowl rather than in the main body.

When I had issues with these carbs awhile back (my jet casings were stripped), a friend of mine had the exact same bike with the latter variation of these Mukini's. I put them on my bike and it started and purred like a dream.

Is anyone else aware of this carb differentiation, why there is a differentiation, and if it affects performance on different bikes or if it doesn't matter (they are same same)?

Thanks!

[phydeauxmutt]

The ones in your first link are typical of the later ones (in the USA), I think it was from '83-on. The '80-'82 models were like your second link.

Why the difference? Nobody knows, but there must have been a reason for the change that made sense at the time.

[Nessism]

The 450 engine was used for many years virtually unchanged. There is no reason to think the carbs wouldn't be both forwards and backwards compatible with different year bikes. I think the bigger issue is getting them properly cleaned and the O-rings updated. Any 30+ year old carbs you come up with should be fully stripped, cleaned, and re-O-ringed with fresh.