the specs you are reading are XZ550 for U.S.A.. But I think they vary by country. If the exhaust is original and good shape. The stock jetting as you stated for 550 works best due the the ODD interior of the exhaust design. I have cut then up. Take my word...very odd.
a) Jet sizes cause a lot of confusion here,
i) because the documentation is a bit crazy
ii) because idiots who work on these bikes seem to put weird random jets in various holes and then sell their bikes because they don't work any more.
iii) because air jets and main jets are the same physical size, so easily mixed up.
iv) because people speaking knowledgeably and correctly about US83 models, will mis-inform people with other models.
v) because some documentation (like the US82 parts fiche) calls both the main jets and the pilot air jets "main jets". The pilot air jets are on the top of the carb, main jets on the side.
vi) because people forget that every time you fiddle with the carbs, you absolutely must check for vacuum leaks, float levels, re-do the synchronisation and mixtures.
vii) because intake, YICS and exhaust leaks make way more of a difference than minor fiddling with jet sizes
Jet specs vary a bit based on what you are reading
Market | Pilot Air | Main Jet | Source | Comment |
Germany 11V | 130/130 | 130.0/135.0 | Parts Fiche / Service Manual | 50PS Model Different Cams |
Europe 11U | 120/120 | 122.5/127.5 | Parts Fiche / Service Manual | |
US RK 83 | 140/140 | 130.0/130.0 | Parts Fiche / Service Manual | Different BD36 Carb |
| 130/130 | 130.0/130.0 | UK Haynes | |
US RJ 82 | 130/130 | 122.5/127.5 | Parts Fiche / US Haynes | |
| 120/120 | 122.5/127.5 | UK Haynes | |
| ?/135 | | Air Box Mod Instructions | |
Australasia 16R | 120/120 | 122.5/127.5 | Parts Fiche / Teardown | Vacuum flapper |
XZ400 14X | 146/146 | 107.5/110.0 | Service Manual | 400 cc model, Difft Cams |
| 145/145 | 107.5/110.0 | Parts Fiche | |
b) The US and German models run larger air jets to lean the bike out to reduce performance and create flat spots to discourage motorcycling, and to lower emissions because of the evil EPA.
The jets are different also to reflect needs of different equipment - Models also have varying Cams, airboxes, carbs
c) Balancing is no problem, but you need to buy or build a manometer. I think there are instructions for building a $4 manometer on Lucky's site xz550.com.
b) The US and German models run larger air jets to lean the bike out to reduce performance and create flat spots to discourage motorcycling, and to lower emissions because of the evil EPA.
?? huh? knew there was a reason, lol
Gentlemen, thank you very much for the information & advice,; I'l be digging deeper into the bowels of by carbs.