Follow along with the video below to see how to install our site as a web app on your home screen.
Note: This feature may not be available in some browsers.
Enjoy XS650.com?Consider making a donation to help support the site. XS650.com receives a small share of sales from some links on this page, but direct donations have a much greater impact on keeping this site going.
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.
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
77 manifolds do not have the vacuum pipe.
-R
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.
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.
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 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.
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.