Why only two carbs on GSX550?

[gearhead141]

Perhaps this is a ridiculous question, but why are there only two carbs on the 1983 and later GSX550E models? The 650 models and up all have four carburetors. I have my suspicions but would rather hear some answers from folks who have been around these machines for some time.

[koolaid_kid]

They are known as siamesed carbs. Each is designed to have enough air and fuel flow for two cylinders. Probably a cost decision. My 240Z had a similararrangement.

[Nessism]

They are known as siamesed carbs. Each is designed to have enough air and fuel flow for two cylinders. Probably a cost decision. My 240Z had a similararrangement.

Different situation to an old Z-car; those used two carbs with one carb throat each to feed six cylinders.

On the second generation 550 Suzuki and/or Mikuni came up with an innovative twin throat carb so only two carbs are used but each cylinder gets it's own carb throat, just like using four individual carbs. In theory this would save money and improve reliability without a decrease in performance. For some reason though the technology didn't catch on within the Japanese motorcycle industry - maybe because some buyers couldn't get used to the idea of two carbs being better than four. Not sure but at any rate, it's not a downgrade in any way. It's just different.

[hampshirehog]

I always assumed it was to try and make the bike slimmer and I seem to remember there was some mention of this in the marketing blurb at the time. Memory might be playing tricks though.

[gearhead141]

My own thoughts...

I thought perhaps they didn't have a small enough carb that would provide enough air flow. As mentioned, it does slim the the bike a bit so that the plastics can be brought in tighter. The down side I see to this arrangement is that it is specific to this engine, i.e. carbs cannot be swapped. Perhaps this is why I don't see too many of the GSX550 on craigslist. If four carbs are desired, a complete head change must be done because of the siamesed intake ports. This brings about the question of swapping in a larger engine; would the original head and carbs need to be retained? Has anyone ever done this on one of these bikes? Would a typical four carb engine have the outboard carbs hanging out? I read a review that claimed the frame could handle more power, so would a 750 motor slip in? I don't currently own a GSX550E but have seen one on CL and am just curious about the bike itself and possibilities for modding it.

[gearhead141]

After looking at Nessism's photos of the 750ES, I have pretty much answered my own question. That bike and the 550ES are nearly twins and the carbs tuck in nicely on the 750. If I'm looking for that type of bike, then I should just keep looking for a 750ES and avoid the pitfalls of the little brother. There is a 550ES in Anaheim, Ca that is being parted out and I had an interest, but I think I'll pass.

[kingofvenus]

After looking at Nessism's photos of the 750ES, I have pretty much answered my own question. That bike and the 550ES are nearly twins and the carbs tuck in nicely on the 750. If I'm looking for that type of bike, then I should just keep looking for a 750ES and avoid the pitfalls of the little brother. There is a 550ES in Anaheim, Ca that is being parted out and I had an interest, but I think I'll pass.

Twins? Those two bikes had nothing in common.

[Nessism]

Twins? Those two bikes had nothing in common.

They were both designed at roughly the same time and share a lot of the same design features, although the parts do not interchange.

[JEEPRUSTY]

I always assumed it was to try and make the bike slimmer and I seem to remember there was some mention of this in the marketing blurb at the time. Memory might be playing tricks though.

its mentioned in the shop manual as well.

It does make for a considerably narrow point in the bike.

Carbs for them are alwyas popping up on ebay some for nearly nothing.It may be that the uniqueness of the design has scared enough people into their being a glut of them on the market.

I do not think you could put them on another bike any easier then you could take "normal' carbs and affix them to the head of the 550

[Steve]

I always assumed it was to try and make the bike slimmer and I seem to remember there was some mention of this in the marketing blurb at the time. Memory might be playing tricks though.

The same type of carbs were used on the KZ1300 that I had.
The engine was already plenty wide, they used the siamesed carbs to try to keep the rider's knees from spreading too far out into the wind.

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