Mikuni BS38mm Carb rebuild - jet size question

[Niels B]

Rebuilding a pair of BS38mm Carb for a '75 XS650B.
i got a set of new gaskets and jet's online, claimed to fit '75 XSB, however looking at the jet size I received they match XS2, TX and TXA main #130 and pilot jet # 42.5.
according to specs the XSB use main #122.5 and pilot jet #45.0

I can decide to use the old once, however the main jet does not show the size, while the pilot jet is the correct size.
anyone have experience with this - assume with the smaller main jet I'll not get enough fuel/air mix.
running stock exhaust.

 

[grizld1]

Don't know what kind of mix-and-match may have gone on or what specs you're reading, but 130 MJ and 42.5 PJ (type BS30-96, metering hole in barb end of jet) is the correct setup for the TX650A and the XS650B (1974-75). 122.5 MJ and 25 PJ (type VM22-210, metering hole in threaded end of jet) is the right combination for XS650C and XS650D (1976-77). If your carbs are linked (one throttle cable) and have separate choke valves instead of a single valve with crossover tube, they're the '76-'77 version.

 

[Niels B]

Well I got the specs from my workshop manual (Haynes) got a full list of the various year and what type used in each carb. but the book may be wrong.
the carbs are ‘75 model - dual throttle and only choke on one carb.
Thanks for the info - I’ll go try these and swab the carbs out and try them on the bike.
The bike is running fine but I never changed the jet so not sure what’s in it now.
The pair I’m refurbishing is an additional set - just thought I would clean them up and keep or sell them when I know they work