1982 XJ550 Maxim throttle shaft seals - or o-rings?

Howdy folks. I've been away for awhile but just got a freebie from my brother so I'm back at it. Actually, this is the bike:

https://www.xjbikes.com/forums/threads/new-member-with-an-82-xj550.66855/

It's been sitting for a couple years now and needs a good bit of attention. First off I'll be doing a full rebuild of the carbs, including breaking the rack and replacing throttle shaft seals. Seems like those seals are nearly impossible to find except from XJ4ever and I don't think I can swing $270 for the complete rebuild kits with seals at the moment so I'm looking at more cost effective alternatives. I've searched through the forums and found that people have used 2 #11 o-rings in place of the seals on the XJ750 Hitachi carbs so I'm wondering if that also works for the Mikuni BS28s on my XJ550. Are they the same size? Does anyone have experience with using o-rings instead of the seals?

 

do not know but i will measure up a few throttle shafts for 550 and 650 and the carb bodies.

you could just get the basics for the rebuild


do not forget that you have to file down the butterfly screws to remove them

 

Thanks for the info. This will be my 4th time rebuilding a set of carbs but my 1st time breaking the rack to do the seals so I'm sure it will be fun!

 

7.92mm dia shaft
11.5mm cup
seal 2.5mm

both mikuni and hatachi appear to have same size shaft and cup diameter for seal

old mikuni seal was 2.5mm thick as was a new hatachi seal

looks like #11 o rings will do it on both carbs

 

One you have carbs fully stripped , they are safe to soak in carb cleaner , I recommend Berrymans carb dip one gallon bucket soak for about 1 hr per carb . One item you really should replace at this stage are the fuel rail interconnect O rings ...you don't want to put carbs back together and have a leak . I have not used the #11 buna O ring myself but some say work fine , the fuel rail O rings are small but buna should work sorry can't give you exact size. After you reassemble do a bench synch , it should get you close to do a running synch.

 

you may also have to replace the fuel tee as the oem tee has no orings on it

 

one dimension was overlooked, the depth of the cavity the o-rings will go in. your sealing against the back wall of the cavity and the shaft, if the cavity is too deep the seal is lost on the back wall, to shallow and you can't get the c-clip on.
now the c-clip, when you use the washer to push the o-rings in, to clip the clip, and that washer is plastic from the 80's , it's going to break. have a very thin metal washer ready.

 

Don't bother with o-rings.

Shaft seals for Mikuni carbs are still available from Yamaha. They don't list them for the XJ series, but I can tell you for a fact these do fit:

Yamaha part 256-14997-00-00

 

Awesome, thanks for the OEM-number. According to earlier posts, these Mikuni shaft seals should also fit the Hitachi HSC33 carb, right?
Best, Nikolai