Carburetor Float Bowl Volume

[Lettuceman]

I have set my 1979 carburetor floats (brass) to the specified 25.7mm height. While still on the workbench, I connected to a fuel supply and filled the bowls to ensure that the float valves cut off the supply. The last thing I do is to drain each bowl’s volume into a measuring beaker and record the volumes. I have 65 milliliters of fuel in each bowl.

The float height is a well-known measurement, are there similar measurements for the optimal fuel bowl volume?

[79XS11F]

I have set my 1979 carburetor floats (brass) to the specified 25.7mm height. While still on the workbench, I connected to a fuel supply and filled the bowls to ensure that the float valves cut off the supply. The last thing I do is to drain each bowl’s volume into a measuring beaker and record the volumes. I have 65 milliliters of fuel in each bowl.

The float height is a well-known measurement, are there similar measurements for the optimal fuel bowl volume?

I've never seen a spec for this in any manual but at least you can be content that all the floats are doing the same thing in each carb.
Rob

[bikerphil]

"are there similar measurements for the optimal fuel bowl volume?"

Some of the later carbs, (ie: 82 XJ) have a nipple on the carb drains in which a clear hose is hooked to. This hose is directed upward and the fuel level can be viewed in the tube. Your carbs are meant to be set by float measurement, so try them at stock level and see how she rides. Then adjust them again higher or lower if necessary.

[Lettuceman]

I like the idea of that technique, so I have been looking for a hose barb plug to replace the float bowl drain plug. It needs to be a 8mm x 1.0 w/barb. Found them at Fastneal for $22.00 each. Ouch! That would be pricey to implement on a 78-80 set of carburetors.

[rpgoerlich]

You could make one with a spare plug and a brass barb for pneumatic line.

[79XS11F]

When I did my dial-A-Jet installation I had to make my own drain plugs with nipples. I soldered nipples into holes that were drilled into the standard drain plugs. The nipples were removed from the Dial-A-Jet plugs that were designed for bowls with the drain on the side but I am sure you could find some cheap 1/8 nipples and do the same thing. So with this setup I can at any time check the fuel levels in the bowls. It goes without saying that they MUST NOT LEAK ...eh.

[DGXSER]

Not sure if the float bowls are the same for all years or not, but the 81 model year was the switch to the side inlet drain plug with the bottom nipple. My SHs both have it. Perhaps you can find some scrap H model carbs to yank the bowls off of and put on the your carb?

[Rasputin]

I like the idea of that technique, so I have been looking for a hose barb plug to replace the float bowl drain plug. It needs to be a 8mm x 1.0 w/barb. Found them at Fastneal for $22.00 each. Ouch! That would be pricey to implement on a 78-80 set of carburetors.

Use a grease Zerk. Drill out the ball and spring, slip a hose onto it and yer done. Costs about 25 cents each. Replace with stock bolw plugs when you are done with the settings. Simple and cheap

[kta]

The idea of measuring bowl volume is a pretty interesting one. It would give a perfect measurement of the float height every time - hmmmmmm.

[XS1100 Newbie]

This measurement is the only one that got my XJ650 right. It has the drin for hookup though. I will do this to the 1100 soon as well, just to see where it is.

[fabricgator]

I've never seen a spec for this in any manual but at least you can be content that all the floats are doing the same thing in each carb.
Rob

4.5mm to 5.5mm below the bowl gasket surface while idling 950-1150 rpm.

[79XS11F]

4.5mm to 5.5mm below the bowl gasket surface while idling 950-1150 rpm.

Thanks Kurt. He is however, talking about float bowl fuel volume not float height.
Rob

[fabricgator]

Roger that.... just tryin to help.

Hey Rob, wasn't it you that gave me that Mikuni book?

[HobbyMan]

Sorry to be a downer here but there are a few variables here that haven't been mentioned. Different gasket thickness are going to give different measurements. Also, not that its going to make a big diff, but tight bowl screws won't give the "exact" reading as loose ones. Probably wouldn't make a diff. Assuming you keep the float the same and measure the volume with and without the gaskett, its gonna be different. If you had all the same gaskets and exactly the same carbs, the measurement might be somewhat relevant. Just another opinion.

[79XS11F]

When fuel levels are set to their normal levels the fuel does not make it to the gasket and the floats are attached to the carb body so they will be unaffected by bowl screw tightness. I believe the plan would be to fill the bowls until the flow is stopped by the float valve. Then drain the fuel into a measuring container and confirm that there is the same amount of fuel in each bowl. What I would like to know is how does one confirm that there is no fuel in the hoses and galleries above the valve that will flow into the bowl as soon as the draining operation is started and the floats fall. Any fuel above the valve will alter the amount of fuel collected.
Rob