wanted, carb flow rate.....

[cd]

or whatever the technical terminology is for how much gas these little things allow in. i really have stayed away from carbs, but this next week im going to read every thread i can find on here, and learn everything i can.... if you want to give me some tips or advice or simple info, thats cool. that being said ive rebuilt several sets of carbs and they worked perfectly once they were rebuilt/cleaned. monkey see monkey do, and i saw myself take them apart, so putting them back to gether was fairly simple. modifying or swapping for other models is where knowledge of all the factors at play is essential. so yeah

[ohgood]

a bunch if if the floats are set wrong


i don't know i've ever seen a rate listed really. the main thing is that that o-rings make good seals, the float bowl seals are tight, the floats are floating (and set proper) and everything isn't worn out.

rust. it hates us, and you already know that. check all the passages.

[cd]

ok, thanks

[MikeNW]

You could probably make a rough estimate...

Say 60 mph and 50 miles per gallon..
That's 60/50 gallons per hour
Or 1.2 gal. per hour
or about 154 ounces per hour
or about 2.5 ounces per minute for both carbs
or about 1.3 ounces per minute per carb, so the gas is hardly flowing!

Much higher gas flow at higher throttle.

That is not a lot of gas! 

Your Own Mileage My Vary etc.

Say 90 mph and (guess) 30 mpg
3 gallons per hour
about 400 ounces per hour
about 6.6 ounces per minute for both carbs
about 3.3 ounces per minute per carb
That's 12 oz per 4 minutes.
Still not a lot.

Is that what you meant? 

[cd]

i hate carbs

especially cheap ones attached to overly complicated fueling systems

efi

[Kurlon]

Using the BSFC formula in reverse, we'll assuming the GS is moderately efficient, and call BSFC .5.  Based on that, at WFO, peak HP (40) you'll use 20lbs of fuel per hour.  A gallon of gas weighs anywheres from 5.8 to 6.5 pounds, so you'll burn anywheres from 3 to 3.5 gallons of gas in that hour.

The CFM flow through the motor is determined by HP x 1.62, or in this case 64.8CFM, or 32.4CFM per carb, again at peak HP, WFO.

[beRto]

Using the BSFC formula in reverse, we'll assuming the GS is moderately efficient, and call BSFC .5.  Based on that, at WFO, peak HP (40) you'll use 20lbs of fuel per hour.  A gallon of gas weighs anywheres from 5.8 to 6.5 pounds, so you'll burn anywheres from 3 to 3.5 gallons of gas in that hour.

The CFM flow through the motor is determined by HP x 1.62, or in this case 64.8CFM, or 32.4CFM per carb, again at peak HP, WFO.

Thanks to Kurlon for the interesting analysis presented above!  I thought I'd elaborate a bit for others who may want to follow along:

background info
Brake Specific Fuel Consumption (BSFC) = fuel mass flow divided by engine power

efficiency = 1/(BSFC*LHV) = max 32% for a gasoline engine (let's assume the GS is less, say 27%)

LHV = lower heating value. This is a chemical property. For gasoline, LHV = 0.012 222 5 kw-h/g

analysis
therefore, working in reverse, we can obtain:
BSFC = 1/(efficiency*LHV) = 1/[(0.27)*(0.012 222 5)] = 303.023 g/kW-h  (or BSFC = 0.5 lbm/hP-h, which is the value Kurlon used in his analysis)

now we return to the original BSFC formula with the following info:

• BSFC = 303.023 g/kW-h
• mass flow = m = unknown variable to be calculated
• engine power = P = 40 hP = 30 kW

BSFC = m/P, or m = (BSFC)*(P) = (303.023 g/kW-h)*(30 kW) = 9038.6 g/h = 9.0386 kg/h

density of gasoline = 737.2 kg/m3 (known value, taken from Wikipedia)

therefore, volumetric flow = mass flow / density = (9.0836 kg/h) / (737.2 kg/m3) = 0.012 261 m3/h = 3.2 gallon (US liq.)/h

conclusion
The GS500 engine, producing 40 hP and having a conversion efficiency of 27%, will require 3.2 gallon per hour to operate.

references
relevant Wikipedia articles:

• http://en.wikipedia.org/wiki/Brake_specific_fuel_consumption
• http://en.wikipedia.org/wiki/Gasoline

comments
The BSFC analysis is theoretical. This approach requires a "guess" on engine efficiency (i.e. 27%) as well as power produced by the engine (i.e. 40 hP). While this academic analysis is interesting, it is probably more valuable to use the empirical data approach (in this case, mpg vs. speed), which implicitly considers inefficiencies and intricacies of the bike being tested.

[philward]

or whatever the technical terminology is for how much gas these little things allow in.

Surely this is a meaningless question?  The whole point of a carb is to allow different amounts of fuel in response to different conditions, thereby achieving the correct air/fuel mix.  If a carburettor was constant-rate it would no longer be a carburettor!