S U carb

[portagepan]

Any advice, experience, feedback on an S U carb for my ' 72 Shovel? It has an Andrews AB cam, Branch head work. A nice solid motor. I have an S&S on it now, but the mileage sucks. I know the CV's are the best for this bike, but I got a nice all chrome "motorcycle" S U with it, so I thought I might try it. The bike has bumped up compression, too.
Thanks. Mike

[bmh]

Wich S&S carb? I have a B on my 71 of similar build. It has always given good milage and performance. Sometimes installing an adjustable air bleed will go a long way to helping both.
Brian

[D.Mac]

SU Carb

Mike,
I ran an SU on a Panhead back in the early 70's. It got about 50+ miles to the gallon, probably could have been better if operated more conservatively. It was always easy to start, even when cold (morning frost on the seat cold). It ran stong, and altitude changes didn't bother it. The engine was a 74, 10.5 to 1 compression, Sifton 412 cam with solids and Sifton springs keepers etc, plenty of fuel delivery for that engine set-up. The only downside is the carb sticks out a bit. I have a '53 Triumph 6T that has it's stock SU, and it also starts and runs great. I think they're a great carb. I don't remember what model SU I used, but I think all I did was change the metering rod. If you could find some bike magazines from the early 70's you could probably get some good info on how to set one up for a Shovel.
Doug.

[portagepan]

Thanks for some feedback. I have an E on mine. The B seems awful big for a 74" motor, unless it was pretty radical. But each bike is different. I think some of my mileage loss may have something to do with the headwork Jerry did. He set them for a strong powerband where the motor runs best, at optimum RPM for the v-twin motor. I couldn't believe how big of jet I had to use to not have the bike stumble at 50 MPH. I do need the chrome metal SU air cleaner, if anybody has one. They are hard to find by themselves. Believe me, I have gone through my E carb and the settings several times, and nothing can be changed to make it any better on mileage that I know of. Besides all that, I just think the SU is a cool carb! But how the bike runs is still my main concern.
Mike

[bmh]

Both the E &B are 1 7/8" carbs. The main difference is the has an accelerator pump. I have an E on another bike , but I shut off the pump on that one. With out the pump the B is a little smoother accelerating than the E. The extra length is most likely the reason. I've always had more trouble with a slide carb than a butterfly carb, so I stick with the S&S. No matter wich you use, tuning is very important. Also gearing has a major effect on milage.
Brian

[portagepan]

I don't know if there is a difference between lore and common knowledge. I am no expert, but I have never heard anything about the B except it was better with big, hot rodded motors, and was too much for a 74. Or maybe they just meant it wasn't needed on a 74. I have never had one myself. The slide carbs are almost fool proof. Very simple, with much better response, and rideability. Bad slide carbs says British to me. The Japanese CV carbs work great!
Mike

[bmh]

I've been running B's on 74 inchers, both stock and modified for 20 years with good results. You might be thinking of the D wich is a 2 1/8 " carb ( so is the G by the way ). A stock bendix is about 1 1/2 ". These measurements are for venturi sizes. not to be confused with throat size. It seems to me an SU is about a 1 3/4" carb, but I'm not sure. The advice I've given on carbs over the years has been that the brand and type don't matter so much as long as size is appropriate. Also you either need to understand how your carb works and how to tune it properly or find one you can. No matter wich carb you choose, if it's not set-up right, it'll never run right. And can cause serious engine damage real quick. Cam and gear selection along with riding habits are usually some of the main points of focus when I help someone pick a carb.
Brian

[portagepan]

Thanks for the feedback. I was just thinking of using the SU because I had it, and a little nostalgia. I am leaning toward the CV, because I have used and adjusted them for a long time, and it is just a much better carb for a v-twin cycle. This '72 is my rider, so I am not so interested in "original". I would say something about the S&S, but I think I will drop it.
Mike

[Early Iron MC]

Mike, I've been running SU's for over 30 years on Flatheads, Knuckles, Pans, Sporty's, Shovels, Evo's and Twin cams, They work great. And they are CV carbs. Thats where Harley got the Idea for there CV.

[portagepan]

OK. I am still looking for a nice, old air cleaner for it.
Mike

[chiefj48]

OK. I am still looking for a nice, old air cleaner for it.
Mike

i've got a complete carb, air cleaner, and manifold for sale.

[portagepan]

Mine is from Rivera. Al I need is the air cleaner. Lst me know if you ever decide to separate.
Mike