Confused on 1975 GT550M stock carb jetting

[TRC]

OK, I'm pretty confused on what the stock jetting is on an American market 1975 GT550M. Every source I look at seems to have different data. One website states the main jet as "either a 100 or 102.5 on all cylinders" while I see flee-bay rebuild kits state things like "Main Jet Size: #75/#87.5" or just "#98 Main Jet" while the Clymer manual says VM28SC main jets are "97.5 center and 95.0 left and right". I have the 1972 carb manual but well, that's 1972. Finally, the oldjapanesebikes.com 550 field guide lists the USA market as "97.5 center and 95 left and right" (chart picture on this page http://www.oldjapanesebikes.com/mraxl_G ... les/page-9) which leads me to believe that this indeed is actually correct. I'm going to be rebuilding all three carbs here in the not too distant future and want to start stock and go from there so then what is actually correct so I can order the parts with confidence?

I'm also assuming I should steer clear of Ebay rebuild kits as it is quite possible that the kit being sold may be correct for some market but not my own (USA)? For example, what do you make of this? I'm assuming that it comes with two main jets so you can install the proper one depending if it is the center or left/right carb? I don't know what to think of the other things in the listing such as a pilot jet size of "#22.5". Isn't stock 25? http://www.ebay.com/itm/Suzuki-Carburet ... 0g&vxp=mtr Also suspicious is that it lists it as fitting both GT380 and GT550 but aren't they different carbs??

Any help appreciated!

[yeadon_m]

Anyone not confused by 550 jetting isn't paying attention
It was the most messed-around with Suzuki triple in the jetting dept (across models with ganged carbs and between countries) yet I've never heard a sensible explanation as to why this was.
First, to why the jets do fit both 380 and 550 carbs: the carb bodies are the same external casting (you can even put 550 carbs on a 380...I have on my 380B and its lovely!), but they've been machine differently for bore (VM24 vs VM28) and the air/fuel passageways. There are also small differences in the float bowls, as the cold starter jets differ, too. But they accept the same type of main and pilot jets, with overlapping sizes depending on model and year.
I have a UK 550B so I cannot really advise on the jets for your US M model. I would advise that you have the outers 2.5 bigger than inner on the main, as that pattern is retained across most models (there is at least one type in an official Suzuki manual suggesting the smaller one is in an outer carb, which makes no sense).
I would use genuine Mikuni and tentatively suggest pilots #25 and mains 100/97.5/100 and then try seat of pants feel to see if you can dial it in from idle through wide open.
Others will probably be along soon and someone may have the same bike, and know for sure!
Cheers,
Mike

[TRC]

Thanks, thought for a minute there that I might have had a screw come loose myself or something.

[Alan H]

That comes as standard with owning any old bike.

[TRC]

I've decided to change my plan of action a bit. First I'll pull the carbs and examine the condition of the jets and clean the crap out of everything and on this first pass I'll just replace all of the rubber o-rings and whatnot and if anything else looks bad I'll replace it individually. I haven't dug into these yet as the bike is new to me so who knows what's even in there currently.

[ConnerVT]

here is the thing about Mikuni carbs - You almost never need to replace the Main or Idle Jets on a stock configured bike. Unless someone decides to clean the brass by reaming it out with something harder, there is nearly nothing that will make them change.

Jet Needles (and to a certain extent, Needle Jets) can wear or pit. And unfortunately, those are the parts which are almost always made of Unobtainium, as they were made to factory specs for Suzuki.

Float Needles and Seats, Bowl Gaskets, and occasionally Enricher (choke) rubber seals, are really the only parts that possibly need to be replaced, even in a 40+ year old motorcycle (unless it was stored at the bottom of the ocean). Step one is always a careful disassembly and thorough cleaning.