carb swap/ HELP!!!

[macnut xj]

I would agree that a single carb would likely not work well due to mixture distribution problems. I'd expect that the two end cylinders would likely run on the lean side. And we all know how quickly a lean condition on an air-cooled bike can cause major carnage! If you have room for a properly designed manifold, you can alleviate a lot of mixture distro problems, but as was said earlier, you can't really do that on a bike. A pair of carbs feeding two cylinders each would probably work well tho. Either something in a two barrel sidedraft like Webers, or even single barrels like SU's or Amal's. My Triumph Spitfire has twin HS2 SU's and they work pretty well, tho I am working on an EFI conversion for it. Actually EFI is really the best way to go all around, but I realize that it's not a simple thing for most folks to do, where a carb swap is. And it's much more difficult on a bike than a car. But, it should actually be pretty easy to make a couple of simple Y- type adapters to adapt a pair of single barrel sidedrafts. Tho the linkage might be a bit of a challenge, I wouldn't think it would be insurmountable.

[ratbyk]

Carb/s Change

Throttle linkage, no problem. Just a slightly longer cable. As long as the outer part of the cable is securely anchored back by the carburetor then the inner cable will pull on the carbs throttle arm easily. Would just have to make sure that you angled the cable "pull" at such an angle that it worked "with the throttle arm.
A single dual throat Weber would work well with each barrel of the carb feeding two cylinders. This set up/these carbs would likely make the bike difficult ride at lower speeds though. Throttle plate changes would have to be minute otherwise throttle response would be very abrupt. This would make for a very jerky ride as you transitioned off and on the throttle.
This abrupt throttle response is the main complaint with putting smooth bores on an XS. OK for racing were you are either wide open or have chopped the throttle (all at high engine speed) but for every day street riding the bike becomes very difficult to ride smoothly. It is either accelerating like crazy or slowing down abruptly.
The smoothness of the throttle response of variable throat carbs like Mikunu's or SU"s is there main feature.
Ken/Sooke