Whats up with my Carbs?

[bryanjnkns]

I'm new to the xs650 and I've read and looked through all the manuals several times over. I have whats titled to be a 76, but I believe its a 77 built in late 76. After looking at several pictures of carbs and comparing them to mine, they looked to be correct for the bike. But after getting into them, I don't really know. I removed the bowls and pilot jet to clean them and noticed the jets were larger than what is listed for a 77, 27.5. At first I just figured the PO swapped them for a larger size.(its got pods and straight pipes) But when I turned over the bowls I noticed an E stamped to the bottom.

I'm wondering if the E stands for the 78 model xs650E? I thought that might make sense considering its has the right pilot jet size for that year. Haven't been able to remove the main jet yet.

Upon futher inspection of the carbs I found other things that didn't quite add up.

The spings in the slides are two different sizes.

One slide has a prong, the other doesn't(sorry for the terminology, didn't know what to call it) If you look closely you'll notice other differences too.

The slides also differe in color. I thought it might be varnish, but it isn't. I'm wondering if the PO swapped a slide and diaphram from another year or replaced it with a new one. But I don't know. Anyones help would be much appreciated.

 

[weekendrider]

The slide with the higher needle and snap ring is from a 78-79 which is jetted stock with a 27.5 pj.

 

[bluebikerblan]

The carbs themselves look to be of the 2FO type characteristic of the 78 & 79 model years. The throat vents as opposed to the external vents of the 76, 77 584 years with external vents. That being so the carb slide on the left of the two pictured looks to be of the 76-77 type. While the slide on the right is of the 2FO type.....how that all occurred and why is anybody's guess. Mine would be that a diaphragm/slide on a 2FO set went bad and somebody replaced it with the earlier (more available type)???

As to the slide springs....While I do recall that the springs are of different lengths (584 vs. 2F0), I don't recall offhand which is which?

Here are a couple of shots to distinquish between the two. The BS 34's of 1980 and beyond are pictured as well.

grizld1 and 5twins carb guide goes into detail of the two types of BS 38's you're dealing with here.
http://www.amckayltd.com/carbguide.pdf

A matching set of "2F0" slides and JBM diaphragms with a good cleaning/rebuild would seem to be the way to go. That would also involve finding and installing 502 jet needles ("tower type) in the 3 position and 27.5 pilot jets.

As is, I really can't imagine how they'd run? Much less how to synchronize ??? BOL Blue

 

[bryanjnkns]

Awesome, thanks blue. I've actually been studying the carb guide for a few days now. But this helps a lot.

 

[bryanjnkns]

Would my carbs function correctly with the mismatched slides, or would I need to replace the 78 slide to a 77. And would they function correctly with slides not intended for the carbs. According to MikesXs the 78 is no longer in production, the website states "Carb slides for 1978-79 XS650s are not interchangeable with
other slides as the needle retainer differs. 1978-79 slides are
currently no longer available." I would really like to be able to use these.

 

[5twins]

You should locate a '78-'79 slide because that's what the carbs are. If you try to use the '77 (or older) type slide, you will need to change all the other jets in the carbs to match that slide/needle combo. What needle is in that older slide? That will narrow down the year it came from. As Blue said, you can get replacement diaphragms for the '78-'79 slides from JBM.

 

[bluebikerblan]

Would my carbs function correctly with the mismatched slides, or would I need to replace the 78 slide to a 77. And would they function correctly with slides not intended for the carbs. According to MikesXs the 78 is no longer in production, the website states "Carb slides for 1978-79 XS650s are not interchangeable with other slides as the needle retainer differs. 1978-79 slides are
currently no longer available." I would really like to be able to use these.

Well Sir.. you have indeed come to the crux of the matter re the BS 38's type II (2F0). While they were/are the favorites of many... trying to get a replacement diaphragm could only be done by getting a replacement slide & diaphragm assembly.....which if you could find them NOS OEM were usually well over $150 each! (Up jumps a rare example) http://cgi.ebay.com/ebaymotors/YAMA...rcycles_Parts_Accessories&hash=item5d2a8b6dd0
Then with the design & production availability of JBM's DIY diaphragms, one could at least repair the assembly by replacing the diaphragm easily and at a reasonable cost. Thus extending the useful life of 78' 79' 2F0 carbs became feasible. But; we are left with the challenge of finding good used slides somewhere. I've found two ways of going: Used 2F0 slides per se or....used 2F0 carb sets as "donors" for slides and other parts as well.

There is a gent in Biloxi "Smith Place" that will on occassion come up with a good variety of 2F0 carb parts and you can watch for those as they may occur. He carries a lot of used carb parts of all descriptions and seems to know his stuff....and prices!

http://cgi.ebay.com/ebaymotors/XS65...rcycles_Parts_Accessories&hash=item43a19414f2

However. I find it more fruitful and reasonable to try to make a good buy on a donor set of carbs like some of those currently available, for example.

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=380360536949&ssPageName=STRK:MEWAX:IT

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=170679356128&ssPageName=STRK:MEWAX:IT

That at least is what I've been doing of late....buying some used sets if I can find them reasonably priced, then designating one to be
a "donor" set and doing my best to set another set on hand straight with collected jets, drain plugs, replaced choke levers, JBM diaphragms etc.
Last time around it took 3 sets to yield 2 good and complete type I's and I've now got 4 more which should yield 3 complete ready for rebuild. Type II's 2F0 this time.

Hope this makes sense? Best, Blue

 

[bryanjnkns]

haha....thanks 5twins and blue.

 

[bluebikerblan]

Would my carbs function correctly with the mismatched slides, or would I need to replace the 78 slide to a 77. And would they function correctly with slides not intended for the carbs. According to MikesXs the 78 is no longer in production, the website states "Carb slides for 1978-79 XS650s are not interchangeable with
other slides as the needle retainer differs. 1978-79 slides are
currently no longer available." I would really like to be able to use these.

To the point of your question....get another 2F0 78'/79' slide with shorter spring, 502-3 needle and Z-2 jet nozzle, equip to stock OEM configuration with new replacement diaphragms, pilots and mains. Blue

 

[DogBunny]

The long spring is approximately 4-5/8" long at rest, and belongs on 1977 and earlier BS38s.
The shorter spring is approximately 4-1/8" long, and belongs on 1978 and 1979 BS38s.

Everything has to match, and that includes the springs.

 

[bryanjnkns]

Thanks again fellas. Appreciate the help. Already have a line on 2F0 slides, springs and jets.