Carburetor ID

[BeetsnGreens]

Hello all. I have a set of carbs that are not original to this bike. I have a 1980 XS650SG. The carbs are BS38's, either the 76-77 model or the 78-79 model. I can't figure out the difference between those two, so help would be greatly appreciated. I may order a rebuild kit, but need to know which one these are. If you need more pictures, let me know. Thanks.

 

[BeetsnGreens]

Also, they have brass floats.
And where are the main and pilot jets? I can easily find them on the BS34's but I'm kinda confused here.

 

[650Skull]

Read through this thread.... http://www.xs650.com/threads/bs38-swopping-needle-jets-and-jet-needles.51676/ ....most of of 5Twins, 2m and gggGarys posts will answer your questions

 

[59Tebo]

Wow! Look at all the barnacles in there! That's gonna take a good scrubbing, fer shure... They look like '78-'79s (more experienced eyes can chime in!). They were considered by most to be the best of them all. What we need for positive ID is a good picture of the other sides of the carb openings, to see the air intake vents. That'll tell ya what year they are.

 

[XSLeo]

Have you read the carb guide? www.amckayltd.com/carbguide.pdf
It has pics showing how to ID carbs.
Your main and pilot jets are in the float bowl. Don't buy carb kits. The only things in there you can use are the gaskets. All the brass parts are wrong.
Mikuni built many variations of these carbs for many bikes. The brass parts in the kits may work with a few of these variations, Just not the XS650 ones.
Better to follow the carb guide to tear down, clean, inspect what you have then determine just what you need then buy just what you need.
Get your brass parts from someplace that sells genuine Mikuni parts. Jet's r Us, Niche Cycle are two.
Mike's sells cheap knock offs for about the same as you can get the real thing for.
If careful you can reuse the stock gaskets.
Leo

 

[gggGary]

tebo's right, intake view is easiest ID
76-77


78-79

but float bowl will tell aso

78 79 on left, earlier bs38s on right, photo 5T's

 

[BeetsnGreens]

Read through this thread.... http://www.xs650.com/threads/bs38-swopping-needle-jets-and-jet-needles.51676/ ....most of of 5Twins, 2m and gggGarys posts will answer your questions

Found my answer there. XS650.com forum noob here. I'll get better with the search bar
.
Thanks!

Wow! Look at all the barnacles in there! That's gonna take a good scrubbing, fer shure... They look like '78-'79s (more experienced eyes can chime in!). They were considered by most to be the best of them all. What we need for positive ID is a good picture of the other sides of the carb openings, to see the air intake vents. That'll tell ya what year they are.

Yeah these carbs are gonna take some work. Here's the air intake:
I did just read the link XSLeo posted. I got 78-79's! Good to hear they are the best. Maybe that's why it's PO switched to em.


Gary- thanks for showing me the jets!

 

[5twins]

I'm going to just point out one little thing. In your 1st pic, notice the carb top screw on the far left is too long. That's because it's in the wrong spot. The longer screws go where a bracket mounts, shorter ones where there isn't a bracket. Your bracket between the carbs is also mounted backwards. The larger cut-out should face the rear. Oops, that's 2 things, lol.

 

[BeetsnGreens]

5twins- thanks for pointing that out! I'll get that fixed.

I have one more question regarding these carbs.
I think this is the idle adjustment screw (the one in the middle and slightly right):

Anyways, that screw is missing from the other side:

It doesn't seem necessary, but is there supposed to be a screw in there?

 

[gggGary]

No, what you show is correct.

 

[BeetsnGreens]

No, what you show is correct.

Much appreciated!

 

[59Tebo]

Yup. gggGary's got it. And, no, being 'linked', the second screw is not necessary. Just make sure you clean up the link hardware, so it's free-moving. Once you get everything all back together, that's how you 'sync' the carbs.