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Sold / Found / Inactive - 78 or 79 BS38 Carbs

Discussion in 'Classifieds' started by Jake650, Aug 21, 2020.

  1. Jake650

    Jake650 XS650 Addict XS650.com Supporter

    My current build is putting a late model electric start motor in an XS1B and the BS34 carbs are longer on the horizontal axis which means the side covers will not fit. I'm looking for a set of BS38s from a 1978 or 1979.
     
    Jim likes this.
  2. Jim

    Jim Beyond the edge is the unknown. Here be Dragons XS650.com Supporter Top Contributor

    I've got a set off a 2FO motor. Don't know if they're original for that motor or not. I'll dig 'em out later and have a look.
     
  3. Machine

    Machine Race the wind Top Contributor

    78-79 BS38s pic.-
    20200410_140147.jpg 20200403_164413.jpg
     
  4. Jake650

    Jake650 XS650 Addict XS650.com Supporter

    Appreciate it Jim
     
    Jim likes this.
  5. Machine

    Machine Race the wind Top Contributor

    There is a long time lingering concern of mine regarding the 78-79 series BS38's which may influence the use of the 78-79's.
    The 78's were the first year of the dual vacuum actuated fuel petcocks. The 78-79 series carbs were also revised to have no float bowl drains. Over the years I've considered this combination of components to be a "system". Concerning fuel flow shut off functions, both the carb needle & seat valve and the vacuum petcocks do this in their own separate way. Almost like redundant systems ?
    Anyway, we mostly all know the importance of effective fuel flow shut off when the XS is parked.
    Can anyone contribute whether it is important or not to keep the vacuum petcocks function in the loop when using the 78-79 series BS38'S?
    I'm looking over my carb inventory here.. 3 sets of BS38'S and 2 XS650 projects :shrug:
    77 manifolds do not have the vacuum pipe.
    -R
    20200822_100452.jpg 20200822_100435.jpg
     
  6. I'm running two old school style petcocks, on-off-reserve, with '78 bs38's on my '77.
     
    Jim and Machine like this.
  7. Jim

    Jim Beyond the edge is the unknown. Here be Dragons XS650.com Supporter Top Contributor

    I'm not well schooled on the 38's so maybe someone can chime in on what year these are. Butterfly's are free and both diaphragms easily pass the drop test. Pretty grody.... but I seen much worse. Should clean up nicely.
    Edit: that's duct tape residue around the bellmouths... not corrosion.
    Edit again: Choke's are stuck closed. I'll let some PB Blaster soak on 'em for a bit and see if they loosen up.
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    Boog and gggGary like this.
  8. Machine

    Machine Race the wind Top Contributor

    Those sure are 78-79's (no float bowl drains) That is a valuable set worth saving. On Motorcycle carbs I've been very reluctant to spray even carb cleaner on em. The rubber components, diaphrams especially, are just very old and too hard to find to allow any unwanted related chemical destruction. Use care.
     
    Jim likes this.
  9. gggGary

    gggGary I'm listening, change my mind XS650.com Supporter Top Contributor

    The reason the 78-9 don't have external float bowl overflows is cuz all carb "holes" were brought inside the air filters, all earlier carbs had vents to unfiltered air at different pressure than inside the filters. This change resulted in more consistent carb function. Those high holes on the intakes are float overflows and will do the job if the slides are shut. (experience).
    @Jim I just ran into a set of BS34s with stuck chokes, ruined one afore I caught on and used heat, second one came out clean when the varnish warmed/melted enough.
     
    Jim likes this.
  10. Jim

    Jim Beyond the edge is the unknown. Here be Dragons XS650.com Supporter Top Contributor

    Just checked it. PB Blaster did it...:smoke: Still kinda stiff, but it moves enough to remove it for further cleanin'.
     
    gggGary likes this.
  11. Machine

    Machine Race the wind Top Contributor

    Well said.now I have a better understanding of the intent to move those "overflows" inside the air filters "atmosphere"
    :)
     
    nj1639 and gggGary like this.
  12. Jake650

    Jake650 XS650 Addict XS650.com Supporter

    I'll be not be using vacuum petcocks so that is pretty much a mutt point for me.

    Jim, is that the set you are willing to part with? If so shoot me a PM.
     
    gggGary and Jim like this.
  13. Jim

    Jim Beyond the edge is the unknown. Here be Dragons XS650.com Supporter Top Contributor

    Sent.
     

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