Float bowl drain plug

[pdqford]

Does anyone know off hand what size threads are on the float bowl drain plugs on my 1980 GS750ET? (Mikuni BS32ss)

I thought they would be metric, but the closest I found at the hardware store was 1/4"-28. Could that be correct?

[bwringer]

No, they're metric -- 6mm diameter X standard 1.0mm pitch.

Of course, who knows what some idiot thumb-fingered PO did to them.

[Guest]

I'll send you a float bowl with the plug.

[Nessism]

The threads are finer than the common 6 x 1, more like 6 x .8 or .9

[almarconi]

Its a 6mm fine thread, 6mm x .75 pitch.

[buckeyemike]

I thought I heard one time they were not all the same? The 750's drain plugs that is?

[Guest]

CV BS carb series 32mm-36mm use the same float bowl and plug.

[bwringer]

Its a 6mm fine thread, 6mm x .75 pitch.

Not the ones on my bike.

[Nessism]

Its a 6mm fine thread, 6mm x .75 pitch.

I just verified using a thread pitch gauge that this is correct.

[almarconi]

Not the ones on my bike.

That's cause your special

[pdqford]

I'll send you a float bowl with the plug.

Thanks for the offer, but I have the drain plugs. I was looking to get four of the correct size bolts so I could drill them out and make a set of wet float level gauge so I could check all four carbs fuel level at one filling.

Its a 6mm fine thread, 6mm x .75 pitch.

Looks like the 1/4" -28 tpi is as close as I'm gonna find. (My calculator converts a 28 tpi to ~.9 pitch.) Maybe they won't leak for the few minutes it will take to check the fuel level.

Does everyone use the $15 Suzuki fuel level gauge? Or do you just go with the dry float setting and say 'good 'nuf'?

[almarconi]

Does everyone use the $15 Suzuki fuel level gauge? Or do you just go with the dry float setting and say 'good 'nuf'?

The fuel gauge is the way to go. I discovered that even if you measure all the float heights the same, it does not necessarily mean you will get the same fuel height.

Mcmaster-Carr sells metric fine thread screws in 6mm x .75 pitch. The have set screws in this size.

[pdqford]

The fuel gauge is the way to go. I discovered that even if you measure all the float heights the same, it does not necessarily mean you will get the same fuel height.

Thanks for confirming what I suspected. Just 'cause the floats appear to be set to the same heights, that doesn't guarantee equal fuel levels.

Okay, I'm finally getting back on this project. Carbs have all been stripped, soaked, washed, blown out with compressed air, and reassembled with the dry float heights set to 22.3mm (to the best of my ability!)

Now I'm ready to set the wet fuel level. I couldn't find a way to hold the carbs while checking the fuel level, so I just hung them temporarily on the cylinder head (where they will end up).

BUT, the carbs are not quite level. (In the picture in the Clymer manual which shows setting the wet fuel level (with clear plastic tubing), the carbs appear to be level.) That is, the parting line between the carb body and the float bowel appears to be close to level, but with the carbs hung on the the cylinder head, my carbs are leaning forward.

So my question is: "Should I jack the front of the bike up to level out the carbs in order to set the wet fuel level?" What do others do?
Thanks for being so patient with me.