RS 34 Float heights, Wet vs Dry

slmjim+Z1BEBE wrote:

daveo wrote:

slmjim+Z1BEBE wrote:

The discrepancy makes no sense until one realizes that the 32mm fuel level spec is the distance from the carb bore centerline to the fuel level in the float bowl.  

Perusing the available documentation of the RS series carbs unfortunately shows no spec for fuel level below the bore centerline. 

Good Ridin'
slmjim & Z1BEBE

The 32mm measurement noted falls in-line with the fuel level being 4mm+/- above the bowl top when utilizing the clear-tube method, with floats set at 17mm per the Mikuni RS manual instructions:

 

   That 32mm fuel level is spec'd in the Z1 White Manual specifically for VM 28SC carbs.  We don't know, nor have we found,  a fuel level spec for distance in mm below the carb bore centerline of RS carbs.  If remembering correctly, there is a (clear tube) spec for distance relative to the bowl mating surface.  Don't assume the 32mm spec in the White Manual is accurate for RS carbs.

Good Ridin'
slmjim & Z1BEBE

daveo post=928695 userid=23775

wrote:

daveo post=928657 userid=23775

wrote:

The discrepancy makes no sense until one realizes that the 32mm fuel level spec is the distance from the carb bore centerline to the fuel level in the float bowl.  

Perusing the available documentation of the RS series carbs unfortunately shows no spec for fuel level below the bore centerline. 

Good Ridin'
slmjim & Z1BEBE

The 32mm measurement noted falls in-line with the fuel level being 4mm+/- above the bowl top when utilizing the clear-tube method, with floats set at 17mm per the Mikuni RS manual instructions:

 

   That 32mm fuel level is spec'd in the Z1 White Manual specifically for VM 28SC carbs.  We don't know, nor have we found,  a fuel level spec for distance in mm below the carb bore centerline of RS carbs.  If remembering correctly, there is a (clear tube) spec for distance relative to the bowl mating surface.  Don't assume the 32mm spec in the White Manual is accurate for RS carbs.

Good Ridin'
slmjim & Z1BEBE

Coincidence?

Mikuni BS34 measures 3mm below carb body

Possibly, but...

🤔


Google query response: 

Thoughts?

TexasKZ post=928700 userid=14419It seems to me that one crucial element has been overlooked in all this; the internal design of the various carburetors. How far down does the emulsion tube extend? How far from the venturi centerline are all of the various jets? 
Also, also, the tilt of the carburetors when installed will affect the clear tube method. IF the top of the fuel bowl is perfectly parallel to the venturi bore, and IF the carburetor is perfectly vertical when installed, then the clear tube placement is largely irrelevant, as the fuel level will be the same all around the carburetor. HOWEVER, most carbs seem tilted, if just a little. This will make the fuel level lower on the intake side than on the outlet (engine) side, necessitating a measurement at exactly the center. Oh, but this will also be affected by the internal design. IF there is plenty of room above the fuel level AND the bowl is perfectly symmetrical in every way, then tilting the cylinder and carburetors forward will make no difference, the vertical centerline will still be the point to measure. On the other hand, if the bottom of the carb body is very close to the fuel height when the carbs are perfectly vertical, then tilting them will make the vertical centerline no longer viable as a measurement point. The reading there will be increasingly inaccurate as the carbs are tilted farther forward.

Also some more, it seems to me that carburetor bowls should never leak, no matter where the fuel level lands. 

Have to ask out of curiosity; how did you determine from the outside that the moveable jaw is at the exact center of the venturi bore, +/- 0.00?  If it's 1mm off vertically in either direction, then the +/- 1mm fuel level variation from the engineering spec of 32mm is no longer valid.
   The question of coincidence?  Maybe.  That's a query for Mikuni engineers.

Good Ridin'
slmjim & Z1BEBE

Wookie58 wrote:

There seems to be a lot of info here for VM and BS carbs but not the RS. The common denominator seems to be 3mm below the bowl gasket surface so I guess that is a good starting point