Dual carb vs single

Cj230k

Cj230k

Location
Massachustts
so I have dual carbs now on my 760, prob is I just found that a previous owner hacked them up pretty good, found a couple crap welds on the mounting flange and then sealed up with maybe jb, so I’m just going to replace them. I see some people running single carbs and love it for the simplicity and others running duals, just looking for the pros and cons of both
Thanks!
 
L

Loganight

Location
Riverside, CA
Not Very good with carbs but I can tell you this. I just rebuilt my 701 and rebuilt the carbs and the tuning has been the biggest pain in my ass, still haven’t finished it. Plus a lot of times carbs have issues so half the carbs half the problems. I’m sure dual carbs have some sort of mechanical advantage( more fuel/ air forced to the engine)but I’m not sure exactly
 
Vumad

Vumad

Super Hero, with a cape!
Location
St. Pete, FL
I am no motor expert, but none of the high end motors experts run single carbs. There is clearly a reason for that. There are always slight variations in cylinders, porting, engine temps, etc. With dual carbs, you can make sure each cylinder gets exactly what it needs. With a single carb, you can not run a cylinder lean which means you always have to run one rich. People spend a lot of money on performance motors on polishing and etc that ensure smooth airflow, but with a single carb, I don't see how there isn't more turbulence at that fork.

Yes a single carb is easier and cheaper, things someone like Yamaha would love, but despite all that extra potential to their bottom line, they still stopped selling single carb motors in 1995.
 
Big Kahuna

Big Kahuna

Administrator
Location
Tuscaloosa, AL
They work well up to 800cc. But above that they just cannot flow enough. I ran a conversion for a while. Stock 44 it was really smooth power. With a TLR Modified 44 (He bored the bottom half to 48mm) the bottom end response was incredible. But not a great setup for cruising or high speed runs. Stuck a few pistons with this setup. 2x when it ran out of gas suddenly!!!!!!!!
 
kevbo

kevbo

Location
dfw
I have had bad luck with high speed lean out using larger single carbs. A 61x case setup seems to work very well with smaller engines, all you give up is a little acceleration when compared to a 62t case with dual 44/46s. Everyone wants bigger but I can say that a pair of 44s work very well and are easy to tune in every application where Ive used them. Standard mikuni 46s are also very good but they tend to require a richer pilot and popoff setting than 44s. It just means more sputtering at part throttle in order to get good response.
 
Quinc

Quinc

Buy a Superjet
Location
California
Dual 46's for every size setup with pipe and porting. Easy to tune and tons of power. Also buy new or close to new carbs, not worth getting someone elses headache and having to buy a rebuild kit and shaft kit. Better off spending the 220$ for new. *If you want more low end punch use reverse jetting.
 
S

Storbeck

Location
Minnesota
Unfortunately you're probably not going to get a very satisfying answer. You're going to have people saying dual carbs are way better, you're going to have people saying single carbs are just as good or almost as good, you're going to have people arguing about what size carb or carbs work best. The overall consensus is going to be pretty much what you expect: there's no question that one carb is simpler, and very few people will argue against some sort of performance advantage of dual carbs, how big the difference is hard to quantify and depends on everything.
 
Pro-pulsion

Pro-pulsion

Location
Ontario, Canada
Interestingly enough if you get a chance to watch Blowsion's old movie Fistful of Foam you'll see Ross Champions freeride ski running a single carb. I did it for a while and didn't mind it but there was a noticeable difference in favor of duals. As long as your jetting, pop off, sealed surfaces are good and airflow is the same on both they're not too hard to setup. The mentioned details are the biggest part of the battle. If one carb is pulling more air in than the other you'll always have tuning problems.
 
DylanS

DylanS

Gorilla Smasher
Location
Lebanon Pa
Cj230k said:
so I have dual carbs now on my 760, prob is I just found that a previous owner hacked them up pretty good, found a couple crap welds on the mounting flange and then sealed up with maybe jb, so I’m just going to replace them. I see some people running single carbs and love it for the simplicity and others running duals, just looking for the pros and cons of both
Thanks!
Click to expand...
Hands down run dual 44 super BN’s on your motor. I ran a 781 for the longest time on them with very close to stock jetting and pop off and it ran very well (with the crossover on the intake mani epoxied too). No need to change anything outside of small jetting adjustments. Wasting a lot of potential on a single carb setup, just put a little more $ and work in to run the duals! Just my opinion!
 
Vumad

Vumad

Super Hero, with a cape!
Location
St. Pete, FL
brapperdoodle said:
Im not gonna lie, Thats the reason i'm afraid of running duals haha Im scared to tune them, too many old motorcycle tuning nightmares :p
Click to expand...

Single carbs don't have the problem because the ski either runs or it doesn't. You tune the single carb to the cylinder that needs the most fuel and leave the other cylinder a bit rich. The problem with the twin carbs is that one cylinder can drag the other and destroy it. Don't leave one carb running lean and you wont have the problem.

I am not expert but I had a single SBN 44 on my X2 and dual SBN 44s on the same motor, and duel OEM 38s on my superjet, and I didn't find the experience of the single to be any amount of an advantage.
 
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