Vacuum Manifold

David Toll

Reliving my youth?
Top Contributor
Messages
587
Reaction score
1,778
Points
143
Location
Gold Coast Australia
Interesting and informative Forum we have going here. The XS is a popular bike Down Under but the distances between owners can curtail face to face interaction so to have so many experts "on tap" is a great comfort.
I am replacing the vacuum petcocks on my '78SE with non-vacuum types as part of a "restoration" project. The carb manifolds have vacuum barbs that I will no longer need. Can I replace the vacuum manifolds with non-vacuum types from JBM Industries? I know I can simply cap them but, in the interest of aesthetics, I would rather the cleaner look.
Many thanks
 
Yep. You can just switch them out.
JBM makes some great manifolds. I use them and have had great luck with them.
The barbed manifolds are great as you can easily sync the carbs using a manometer. JBM use to sell them, but no longer do. But if the barbs are worn out and egg out the hole they can leak and cause problems.
 
I agree with littlebill31. Those barbs are very useful to use a manometer to sync the carbs.
I would not replace them. I use a length of fuel line, that runs from one barb to the other. That closes them off.
 
I believe you will find the 78 SE carbs have vacuum ports. So you could eliminate the barbed manifolds with no issues.

full


The slotted screw just above the throttle shaft covers the port. It's a bit tight so getting an adapter in there might take a bit of fiddl'n so it doesn't bind the throttle.
 
Thank you gentlemen. I will retain the original manifolds with barbs as installation of a vacuum port in the carb body is a bit tight on the throttle assembly as Gary has indicated. As I approach carb sync time I'll post again to seek insight into this "manometer" business. I have read most of Grzld1 and 5Twins carb guide but the humble carburettor remains terra incognito at the moment. Your timely advice is greatly appreciated.
 
Last edited:
Fyi David, there's a few active owners in the SEQ area.
Cheers,
Phil
Glad to hear that Phil. Have considered joining the XS 650 club but the focus seems to be in NSW. Thought I might be looking at riding with the Ulysses boys. Nothing wrong with those lads except for their unwarranted predilection for Davidsons and Trumpies. Wont have the SE back on the road for a few months but will be happy to stay in touch with local enthusiasts from SEQ to seek advice and stay abreast of upcoming events.
 
The carb guide will make more sense out of the carbie once you dig in. Welcome. Pic of your mc?
 
Here she is. My first XS. Great condition and really only a general cosmetic refurbishment but I want her back as close to original as possible. Cost me $4500 which is not bad in this country especially in this condition. American import so importer probably paid $450 for it there but I'm happy. Rode Yammies and Dukes before but nothing with the class of this old dowager. Have replaced the pods with a set of original air boxes. Will rejet the carbs back to original, (great info for that on this forum). I'll replace the wiring harness which is bare and melted in places and put on an original headlight. Probably keep the coils, points, regulator and rectifier system so I can relive the days of setting the points on the family EH with my old man. I have bought replacements for these items. Handle bar switches need replacement as do the tyres which I believe may be original (only 20K miles on the machine). Will do the brakes and locate an original front master as well. New swing arm bushes, steering bearings and repainted rims. Will do the front forks and the rear shocks have to go. Finally, the tachometer may need a rebuild. Will hang onto the 2 into 1 pipes as they give her a great sound. Have been cleaning off the rust and repainting the frame as I pull things off. Only rattle can work but I'm using the good stuff with a proper primer. A couple of items need rechroming and, of course, I'm shaving by my reflection in the polished cases. Fortunately, the motor runs strong, clutch works properly and the starter does what it should with a little help from a new battery. First time I've listed all the probabilities - doesn't seem too bad on paper. The hardest part is waiting for the bits to arrive from Geoff's or Mikes XS, (and paying the postage). Can't wait to get her back where she belongs! Sorry 'bout the image quality but I didn't take one before I started pulling bits off so this is from the sale advertisement - gives you the idea though. Thanks for your welcome and interest.
 

Attachments

  • XS'78.png
    XS'78.png
    877 KB · Views: 143
Last edited:
Good looking bike there David! Keep whacking away at her. For me , the electrical work is the most challenging. They really are a labor of love aren't they? Good luck and post pictures as you go!
 
Back
Top