Identify these carbs for me, please

[Take Warning15]

I thought that these were 1979, XS650 carbs. Now I'm not sure. It has 27.5 pilot jets, and 137.5 mains.
Can anyone tell me for sure what these are and how they should be jetted and adjusted (stock)?

 

[5twins]

They are '78 or '79 carbs, but those aren't the "D" model (that would be a '77). They would be from an E ('78) or F ('79) model. 27.5 is correct for the stock pilot size in them. Here's the jetting and settings for the U.S. carb sets .....

 

[Take Warning15]

Well that makes a lot of sense. It was running pretty well but the right side was popping a bit and both plugs are always dry black. Could this be the main reason or might there be more that I'm not seeing? Thanks.

 

[5twins]

Could what be the main reason for what? If the carb set in being used on an all stock bike, you probably don't need the 137.5 mains. That's one size larger than the stock 135. Other causes of rich running could be wrong float settings or bad o-rings on the needle jets. Since the mains were changed, someone's been into those carbs and fooling with them. You should probably also check and verify that the needles are set to their proper #3 slot.

 

[Take Warning15]

Okay, great. I did try to check the needle but my snap ring pliers are a bit to bulky to get in there. I'll have to find another pair and check. Thanks!

 

[Take Warning15]

Hey 5Twins, would you happen to have a breakdown of the 78-79 carbs? I just need to see the needle assembly. I have a spring, a washer, a circlip, then another little plastic bushing. Is the washer supposed to be in there or is that something the PO did to get half a circlip position.

 

[member3480]

Heres a link on the breakdown...
http://www.yamahapartshouse.com/oemparts/a/yam/50041b84f8700209bc785ceb/carburetor-xs650-e006501-f

 

[Take Warning15]

thanks. Here is what I'm looking at. I don't see that washer in the breakdown. However, it looks necessary because the spring is so big. It nearly slips over the circlip. Is it the wrong spring? The breakdown looks like it shows a smaller spring.

 

[5twins]

Yes, although the drawing doesn't show it, there is a washer between the spring and e-clip, probably for the very reason you mentioned. Also, maybe to keep the spring from working against and possibly dislodging the e-clip .....

Do my eyes deceive me or am I seeing your e-clip in the #4 slot, one step richer than stock? If that's the case, that would explain your black plugs. You run in the midrange and "on the needle" for the majority of your riding time so its setting has a big effect on plug color.

 

[Take Warning15]

That is correct. I know it should be in position 3. I also ordered the proper main jets. I'll try both corrections and then see what happens.

I do have UNI pod filters and aftermarket exhaust so I'll start from square one. At least I know why it has been running rich! Thanks.

 

[5twins]

Well, with pods and pipes, you'll probably need slightly larger than stock mains anyway. The 137.5s may be good but I'd try a 140 as well just to be sure. Like I said, it wasn't the mains making the plugs black, it was the needle setting. In fact, with larger mains, the needle usually needs to to be set one step leaner than stock, in the #2 slot. When you do that, many times it creates a flat spot just off idle and one step up on the pilots is needed.