Speaking of CFM, someone mentioned 650 CFM, but some of these carbs seem to be a lot smaller than 650, more like 165 or 175. I know it makes a difference. Is that the gas fuel/volume? or the size of the plenum?
CFM flow for the GL-1000:
RPM @ 100%[email protected]
75%VE (VE = Volumetric Efficiency)
1000 rpm = 18 cfm = 13 cfm (I say 75% for myVE, not yours..)
2500 rpm = 44 cfm = 33 cfm(cfm is a measure of demand)
4000 rpm = 71 cfm =53 cfm
6500 rpm = 115 cfm = 86 cfm
8000 rpm = 141 cfm = 105 cfm
A Weber 32/36 DGV flows 255 cfm...
The primary (32) flows about 190 cfm...
The secondary (36) flows the balance when activated.
The throttle progression is: primary = 1st 2/3: secondary = the last 1/3 (...roughly).
There is a fairly quick transition from primary to secondary.
So... knowing what the motor will flow, and its operating rpm range, tells us how much carburetor we need, and how much we don't need. (...of course it's simplified)
If the above is taken as gospel, then we see that the 32/36 DGV may be more carb than we need. Looking at Webers chart below says we're 'bout right on the money though.There are any number of variables (erroneous inefficiency is one) that allow for error in trying to calculate with accuracy. My Weber sits on a 8-rubbered Type-3 manifold, and I aint calling that efficient by any standard, but it works.
I'd be happier with a smaller carburetor on my bike, but what I've got works for now.
Here is my
Weber chart with input: (others may differ)
Line #1 = redline @ 9500 rpm
Line #2 = factory spec max pwr @ 7500 rpm
Line #3 = where I'll normally highside my upshift when tooling around.
Line #4 = one cylinders capacity...
Weber has other charts, but this one is a good start for us.