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GS550 carb swap

  • Thread starter Thread starter CovictJoe
  • Start date Start date
C

CovictJoe

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Hey Guys

I'm building a 1980 GS550E and I recently picked up 2 1991 Katana 750s for parts bikes, I plan on using the front and rear ends on my GS.
However I was wondering if it would be worth it to use the Katana 750 carbs on my 550 engine, the carbs seem to be slightly bigger and are a newer design so it seems like a nice upgrade.

one of the Katana's also has a really nice 4-to-1 Yoshimura exhaust that I want to use.

does anyone here have experience using Katana parts on GSs?
 
If you don't want the carb you're replacing, I'll take it. I'm still having issues with mine.
 
The '80 GS550 uses Mikuni BS32 carbs which are the same model and size as used on the 750 and 850's, which is another way of saying they are plenty big for your 550.

Carb rebuild tutorial linked in my signature.
 
As Nessism mentioned (and sort of hinted), unless you are "building your engine" by boring it and stroking it beyond its limits, the stock carbs will handle it quite well. It is common to put the top end of a 650 on the 550 cases, I don't know how much more you can go than that. Well, yes, I do know.

Stock displacement on a 550 is actually 549.7cc.
If you bore the cylinders 3.0mm (I have no idea if that's even possible or practical), displacement would be 610.2cc.
If you install a 650 upper end (stock bore), displacement would be 673.9cc.
If you bore the 650 cylinders 3.0mm, displacement would be 740.6cc.

Note that all of these are still less than the 843cc of the 850, which uses the same carbs, but with different jetting.

.
 
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