Single Or Dual Carbs

GIL

GIL

Power In The Hands Of Few
Location
Cullman AL
Big Kahuna said:
LOL

Here is my take. You cannot leave well enough alone!!!!!!!! You had a good setup. Even Charles said so!!!!!!!


LOL, Just busting your chops.
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I know, but, I love to tinker! I love to experiment! Who knows, maybe someday I can re-invent the wheel. LOL
 
steveyz250fpilot

steveyz250fpilot

Banned
Location
Huntsville, Alabama
It would be neat to see some type of chart that has bore and stroke and rpm and then equates that to cfm of air/gas necessary at the rpms and then states what each certain bore of carb will sustain. My carburetor knowledge is very slim. I know setups that I have ridden that have singles and duals that both run good. On this board, there's a lot of so-and-so said this so that is what I preach. I have never had the desire to get into the physics of carburetors and what motors need from them, but it would be neat to have some cold hard facts. :Banane37:
 
Matt_E

Matt_E

steals hub caps from cars
Site Supporter
Location
at peace
yz250fpilot said:
It would be neat to see some type of chart that has bore and stroke and rpm and then equates that to cfm of air/gas necessary at the rpms and then states what each certain bore of carb will sustain. My carburetor knowledge is very slim. I know setups that I have ridden that have singles and duals that both run good. On this board, there's a lot of so-and-so said this so that is what I preach. I have never had the desire to get into the physics of carburetors and what motors need from them, but it would be neat to have some cold hard facts. :Banane37:
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I gave up on that, myself. Decided to have a pro build my motor and go with whatever he says.
 
SuperJETT

SuperJETT

So long and thanks for all the fish
Location
none
yz250fpilot said:
It would be neat to see some type of chart that has bore and stroke and rpm and then equates that to cfm of air/gas necessary at the rpms and then states what each certain bore of carb will sustain. My carburetor knowledge is very slim. I know setups that I have ridden that have singles and duals that both run good. On this board, there's a lot of so-and-so said this so that is what I preach. I have never had the desire to get into the physics of carburetors and what motors need from them, but it would be neat to have some cold hard facts. :Banane37:
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701 @ 7000 rpm if you're just going by displacement equals 173cfm. Even a 44mm can supply all of that.
992 (90mm on 10mm stroker) @ 7500 rpm is 262cfm.

Based on this older article http://www.groupk.com/tec-carbs99.htm even a single Buckshot 44 can handle that theoretically.

Real world performance is different because a 2 stroke is not constant air flow plus a ton other things.

One other thing, are you really worried about max airflow for top speed?
 
weston

weston

Location
Oregon
stuff and thing

hangtime said:
I noticed at Daytona that very few surf riders have twin carbs .
I'm having a carb problem and instead of rebuilding the ones I have I was thinking about switching to a single and buy brand new.

What does everyone use ,44 .46,48 ??
My motor has a B-pipe limited and I'm gonna get an MSD enhancer.

I like the idea of simple and easier to tune but dont want to sacrifice any bottom end.
Thanks for any advice :biggrin:
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YA YA DUAL 44 makunis best bang for your buck
 
steveyz250fpilot

steveyz250fpilot

Banned
Location
Huntsville, Alabama
SuperJETT said:
701 @ 7000 rpm if you're just going by displacement equals 173cfm. Even a 44mm can supply all of that.
992 (90mm on 10mm stroker) @ 7500 rpm is 262cfm.

Based on this older article http://www.groupk.com/tec-carbs99.htm even a single Buckshot 44 can handle that theoretically.

Real world performance is different because a 2 stroke is not constant air flow plus a ton other things.

One other thing, are you really worried about max airflow for top speed?
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facts! Am I personally worried about max airflow for top speed? Not at all. I might do a 3-4 second wide open run every once in a while, but I'm personally interested in what is better for a low end response.....without lacking anything getting to the top end. As far as sustained top end.... I have no desire for that, but information is interesting.
 
Big Kahuna

Big Kahuna

Administrator
Location
Tuscaloosa, AL
yz250fpilot said:
facts! Am I personally worried about max airflow for top speed? Not at all. I might do a 3-4 second wide open run every once in a while, but I'm personally interested in what is better for a low end response.....without lacking anything getting to the top end. As far as sustained top end.... I have no desire for that, but information is interesting.
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with a single you just are not going to get both.... You will be able to get to the top end, but not for any lengthing of time.... 3-4 seconds can be long enough to lean it out on top....... Been there, done that.

You could set the Carb to give you more top end capability, but your bottom end performance will suffer.

Heck, Jett had a Novi with no high speed jet (removed) and he still could not get it rich enough up top.
 
750SX

750SX

DO IT
Location
Palmyra
IMO Having a single carb is like taking your dual carb manifold and making each of the plenum's twice as long. I say this because negative pressure has to be made on each side of the carb in a single carb setup, instead of having one direct route like in a dual carb setup. This causes a drop in signal to the carb, resulting in less performance.

My question is: If a single is just as good or better than duals, why did yamaha go from a single carb based motor to duals?
 
GIL

GIL

Power In The Hands Of Few
Location
Cullman AL
My question is: If a single is just as good or better than duals, why did yamaha go from a single carb based motor to duals?[/quote]

good point for the defense of 2!
 
2

2XLR8

X-
What you really need to ask your self is why they went from the 38's on the 81 mm bore superjets and the waveraider 1100 to the 44's on the 84 mm bores 760's and gp1200's. When the 760's and 1200 were being developed there is no reason why mikuni could not build anything in between such as 40 or 42mm carbs for yamaha. Mikuni builds what the manufacturer asks for and we buy it as aftermarket from the same castings from mikuni. So here we are modifying or craft a heck of a lot more than stock and we still want to run a single? I don't get it.
 
steveyz250fpilot

steveyz250fpilot

Banned
Location
Huntsville, Alabama
The real question that I want to ask is...

How does my boat, running a single 48, hit harder than the other 5 mil strokers that I have ridden that had dual 46's and dual 48's? 99% of the people on here have denounced a single carb setup, but anyone that has ridden my boat since it was tuned properly stepped off stunned.
 
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