Single Or Dual Carbs

[ski4]

so would dual 46's taperbored be over kill for a 701 that is piped, ported etc?
just cuz i have that, i hae a manifold and the extra 46 on a shelf just needs rebuilt

i don't often hear that combo, usually 44's or 38's

 

[Matt_E]

Pay close attention to jetting, adjust, adjust, adjust, and measure popoff.

 

[waxhead]

i have sey up a songle 46 on a ski that had the same portjob and pipe as my ski
i had twin 44
they had a single 46
Mine would kick its ass for low end reponse and power
both skis were ported 701 with b-pipes and msd
milled heads,
both were surf skis
the really bad thing about the single was it would go flat up top straight away
so you would go for a wave gas it and it would pull though not well and then it would taper off up top

 

[hangtime]

I didnt think this much discussion would ensue over a simple question .
I'm really torn now as there are good points for both setups .:banghead: :banghead:

I don't see how another carb would give you more horsepower ,I'm only running a stock 701 (not ported) with a b pipe and I will add an MSD enhancer .
It's still the same motor with the same compression and same stroke, same gas.does it rev higher or what ??

I don't hit high end in the surf but once in a while at my dad's lake I ride full speed and would like to be able to toast the one other standup guy on the lake .:headbang:

 

[Matt_E]

Another carb doesn't necessarily give you more HP.
But two carbs instead of one can make the fuel delivery more efficient, for one thing.
The breathability of the motor will be better at mid and high RPMs, where a single cannot keep up due to air flow restrictions.
As you may know, horsepower isn't one set number for the entire RPM range.
It's a very dynamic curve, the number changes with RPM.
Dual carbs will provide for a higher integral of that curve, ie more area under the curve, ie more HP at mid and high RPM points.

 

[Mile9c1]

It's simple, if you have 61X cases, run a single. If you have 62T cases, run duals.

Maybe you guys are confusing "bottom end" with "throttle response". Because the instant you hit the throttle your RPM's jump to 3,000-4,000 (I'm talking instantly). Look at a tachometer (this is the only thing couches are good for, lol), you'll see what I'm talking about. So where exactly is the "bottom end"??

I think duals will give you better response in the bottom end, if they're tuned correctly of course. A carb has two modes of operation, the low speed circuit and the high speed circuit (or the pilot circuit and the main circuit, whatever). While in the low speed mode, the signal on the jets mainly comes from engine vacuum NOT airspeed. This is simple carb physics, it's not debatable.

A carb really doesn't have much to do with power at all, it just has to feed fuel into your engine to match the rate of airflow. That's it! The ratio it needs to feed in is always a constant 14.7/1 or so. Your porting and your exhaust setup have a far far far greater effect on power than you carb does. The only thing you carb can do is hurt power, if it's not tuned correctly (which is your falt, not the carbs).

 

[Matt_E]

Air flow. That's what I said. Look closely, it's hidden in all that garbage I typed.:biggrin:

 

[Takeastand SJ]

I recently switched from dual 44's to a single 48 powerbomb and couldn't be happier. People that say you can't run them wide open don't know what they are talking about, ya you can't go run wide open for a half an hour but it is more than enough for the surf. Setting the carb up right gives your motor more than enough gas, external fuel pump, right size return line restrictor, etc is all it takes.

 

[Takeastand SJ]

i have sey up a songle 46 on a ski that had the same portjob and pipe as my ski
i had twin 44
they had a single 46
Mine would kick its ass for low end reponse and power
both skis were ported 701 with b-pipes and msd
milled heads,
both were surf skis
the really bad thing about the single was it would go flat up top straight away
so you would go for a wave gas it and it would pull though not well and then it would taper off up top

Good example of a single carb not tuned correctly.

 

[SuperJETT]

I recently switched from dual 44's to a single 48 powerbomb and couldn't be happier. People that say you can't run them wide open don't know what they are talking about, ya you can't go run wide open for a half an hour but it is more than enough for the surf. Setting the carb up right gives your motor more than enough gas, external fuel pump, right size return line restrictor, etc is all it takes.

I ran a single Novi 48, tiny restrictor jet, biggest Mikuni fuel pump, and even with the main jet COMPLETELY OUT OF THE CARB I couldn't get the thing to richen up on top and ran lean. On my setup, a lot of it had to do with how Novi sets their carbs up, they alter the fuel path to make them more sensitive for 1 carb per cylinder setups, which then limits max fuel flow for a single carb setup.

 

[orange flattop freestyler]

This is aways an interesting read but for the record,

i run twin 48mm Riva power bombs on my freestyle boat and they hit harder than any other carbs ive ridden on,

 

[Matt_E]

This is aways an interesting read but for the record,

i run twin 48mm Riva power bombs on my freestyle boat and they hit harder than any other carbs ive ridden on,

That carb picture is very....:hail:

 

[Big Kahuna]

I recently switched from dual 44's to a single 48 powerbomb and couldn't be happier. People that say you can't run them wide open don't know what they are talking about, ya you can't go run wide open for a half an hour but it is more than enough for the surf. Setting the carb up right gives your motor more than enough gas, external fuel pump, right size return line restrictor, etc is all it takes.

Hmmmm let's see..... TLR started the single craze with Rick Roy's setups.......... He did my porting............ stated that with his porting (or any porting) that he recommended a single setup (using his modified carb) that the throttle response would be incredible, but Do Not Run WOT with this setup or any single carb, that it could not safely provide enough fuel at higher RPM's......( Understand, this is with using 62T Cases), the motor would lean out..............

 

[Takeastand SJ]

Hmmmm let's see..... TLR started the single craze with Rick Roy's setups.......... He did my porting............ stated that with his porting (or any porting) that he recommended a single setup (using his modified carb) that the throttle response would be incredible, but Do Not Run WOT with this setup or any single carb, that it could not safely provide enough fuel at higher RPM's......( Understand, this is with using 62T Cases), the motor would lean out..............

So the 100 times I have ran my motor (62T)wot for 10, 20 seconds at a time has hurt it somehow? Sickerlings 900 with a single 46mm carb doesn't work? Taylor Curtis won O-side never running his motor wot? I'm not going to argue with you, if a single carb is set up right you can run it wot for short periods of time with no problems.

 

[Matt_E]

So the 100 times I have ran my motor (62T)wot for 10, 20 seconds at a time has hurt it somehow? Sickerlings 900 with a single 46mm carb doesn't work? Taylor Curtis won O-side never running his motor wot? I'm not going to argue with you, if a single carb is set up right you can run it wot for short periods of time with no problems.

Bingo.

 

[Idok]

st. aug crew runs singles ONLY...granted none of us are running stroker motors...






there is also a diff between pinning the throttle, and an actual WOT run........I run WOT in the surf all the time, but hardly EVER allow the rpms to fully wind out for a wot run on the flat stuff.....

 

[ski4]

Good example of a single carb not tuned correctly.

unfortunately it was as close as could be, there were many leaks in the cases taht eventually lead to detonation and a 4 corner seizure
it was a highly overcompensated set up that still was not quite on. but i also have heard running the line between detonation/lean and normal is where the best performance is

 

[Big Kahuna]

So the 100 times I have ran my motor (62T)wot for 10, 20 seconds at a time has hurt it somehow? Sickerlings 900 with a single 46mm carb doesn't work? Taylor Curtis won O-side never running his motor wot? I'm not going to argue with you, if a single carb is set up right you can run it wot for short periods of time with no problems.

What kind of porting do you have............ I am not saying it impossible, just not adviseable............ I ran a single for a year and loved it, but swapped to dual 44's, even better now......... I could go back to a single tomorrow with no hesitation.

Who said anything about arguing? this just a good debate.
:Banane01: :Banane01: :Banane01:

 

[WaveDemon]

I don't know how an undersized carb can lean out a motor. The throat of the carb will only allow so much air to pass through. It would have to be a poorly designed carb to not allow enough fuel to match airflow at 14.7:1 ±

 

[waxhead]

I don't know how an undersized carb can lean out a motor. The throat of the carb will only allow so much air to pass through. It would have to be a poorly designed carb to not allow enough fuel to match airflow at 14.7:1 ±

I made this point over at pwctoday

Basically i said do you think mikuni is silly enough to make a carb that can flow more air than it can flow fuel

That would be silly and asking for law suits for blown engines