Single Or Dual Carbs

[Matt_E]

:biggrin: Hey, I am happy for you. What'd Paul tell you? Is the damage not bad, or non-existant? Details man, details!

I just brought my cylinder to the shop to get it bored. I did some porting updates :biggrin:, and it needed to be bored anyhow. Going to 83mm.:arms:

 

[Mile9c1]

By trying to flow the same air through a single it increases the velocity and delivers fuel air faster or so they say.

That is one theory, but there are other theories that don't support the single. Like some say if you are running a single, that when one reed set closes, the air/fuel charge turns around and starts to get sucked into the other cylinder. So the air flow actually slows down/gets messed up.

Also, if you compare say a single 50mm carb to dual 38's, you will have very similar air velocity in both setups. Almost dead nuts the same. However, the duals will have twice as many metering orifices, so they can be more precise and more responsive (in theory).

I don't know much about carbs, I don't think many people do, but it seems like dual 38's or 44's for a 701+ cc engine aren't too big. Look at little 125cc dirtbikes, they run 37-38mm carbs.

 

[waxhead]

hey i am running dual 48s on mine

When you close the reed valve you also get a sonic wave up the carb

this will effect the single as well

 

[ski4]

some say you save some fuel with the single as well, but i ran with my single 46 and burned a lot more than similar set ups with stock duels and didn't have the top end
wait i had a huge air leak and was way over compensated trying to richen the mix


i guess i can't say for sure

 

[ski4]

so by the way, anyone have a dual stocker set up to part with? :frown:

 

[waxhead]

lets get the facts sorted
if you use less fuel with a single then its because
a: you have less power and dont need as much air/fuel mix
b: you are running leaner than before
if its b then you were ethier to rich before or now you are to lean
and so you cant compare

 

[Mile9c1]

Duals will meter more effectively since they have twice as many fuel holes. So that should make them more efficient (given similar power levels).

Mikuni says a single 44 is only good up to 80 horsepower.

 

[ski4]

lets get the facts sorted
if you use less fuel with a single then its because
a: you have less power and dont need as much air/fuel mix
b: you are running leaner than before
if its b then you were ethier to rich before or now you are to lean
and so you cant compare

actually my facts are pretty straight, came with a single, 46, ran through more gas than a similarly set up dual 38, ( a lot)

had a big air leak in the cases ( from the a-hole i bought it from after his silicone seal failed)
needed to get much more rich to avoid detonation,

so i really can't say if a single is much more effiecient than a similarly prepped dual . it is supposed to be from what i hear but i can not prove it from my personal experience.

so you either mis read or mis interpreted what i meant

 

[unclehulka13]

thats completely true. My boat wouldnt run with a stock 44. i had to get it bored out. If its a correctly modded single, i'd be willing to bet the hit is just as hard as with duals.
I had those crappy i body mikunis that look like keheins, and those blew ass. I might try dual 44's this year, just for testing.

 

[Mile9c1]

Those I bodies don't have a good singal, according to Group K.

 

[ski4]

thats completely true. My boat wouldnt run with a stock 44. i had to get it bored out. If its a correctly modded single, i'd be willing to bet the hit is just as hard as with duals.
I had those crappy i body mikunis that look like keheins, and those blew ass. I might try dual 44's this year, just for testing.

that is what i had always heard too, and my taper bore 46 was supposed to do tht for me, it hit hard but died out early on the top end

but like i said , there were some other problems limiting things too on this motor, so i can't say where the fault really was

but for ease of tuning single wins

 

[Big Kahuna]

thats completely true. My boat wouldnt run with a stock 44. i had to get it bored out. If its a correctly modded single, i'd be willing to bet the hit is just as hard as with duals.
I had those crappy i body mikunis that look like keheins, and those blew ass. I might try dual 44's this year, just for testing.

are your referring to your Kawi or Yami?


I ran a stock single 44 on my SJ a few years back (ported and stock cylinder), ran perfect, barely had to do any tuning............ The I Bodies work well on the SXR's, Tim Zarnsdorf has a pump gas limited that freaking rips your arms off using the OEM I Bodies.......

 

[unclehulka13]

my kawi wouldnt run with the stock 44. i was gonna use it for breakin, just so i wouldnt go crazy and roast anything, but it would barely run. I put my modified 44 on, and it was night and day difference.

zarnstorff knows alot, but since Keith is so close, i went with what he suggested, and i would go back to those i bodys

 

[Big Kahuna]

how much did you play with the jetting/ popoff? no reason for it not to run.......

 

[waxhead]

actually my facts are pretty straight, came with a single, 46, ran through more gas than a similarly set up dual 38, ( a lot)

had a big air leak in the cases ( from the a-hole i bought it from after his silicone seal failed)
needed to get much more rich to avoid detonation,

so i really can't say if a single is much more effiecient than a similarly prepped dual . it is supposed to be from what i hear but i can not prove it from my personal experience.

so you either mis read or mis interpreted what i meant

It wasnt aimed at you
was just to put the whole thing in perspective

 

[ski4]

right on
i got ya

 

[unclehulka13]

how much did you play with the jetting/ popoff? no reason for it not to run.......

back then, any was too much.
now im a bit more seasoned, so i can get them spot on usually within a few tries..


my carb now has a bigger low speed jet than a high speed.

 

[WaveDemon]

lets get the facts sorted
if you use less fuel with a single then its because
a: you have less power and dont need as much air/fuel mix
b: you are running leaner than before
if its b then you were ethier to rich before or now you are to lean
and so you cant compare

a single 44 WILL use less gas at WOT because it is smaller...

 

[waxhead]

a single 44 WILL use less gas at WOT because it is smaller...

what about if the engine is making say 80ho on a single and a dual
are you saying the dual will use more gas

 

[kid4now]

I run a single 44/48 tlr modded carb and love it ( Watercraft Factory does the same mod). It always runs. If need be I can pull it off go through the whole carb and reassemble and install a very short time. When the weather changes from warm to cold, humid to dry its real easy to readjust the low and high speed if necesary. One less thing to fail.

I run a ported 61x cylinder, 62t cases with all the bolt on goodies and it hits hard and crisp. For freeriding or freestlye its my choice. If you are going to race, run wide open alot or have a hugh monster motor like pauls and need to move alot of air of course duals are the way to go.

For reliability, good performance, and easy maintenance a single is the way to go.

Just my 2 cents worth.

Brad