Fuel Level

[SouthernGrey64]

Hi all,
It’s been a while since I posted last and have really been enjoying my bike since restoring it in 2015. You guys were a great help then in getting it back on the road after sitting in the basement for 22 years.

I have a question about fuel level. I have just rebuilt the carbs on my 1979 XS100 SF. I set the float heights at 25.7mm and then checked the actual fuel level. The fuel level seems to be right at 4mm down from the top of the float bowl with little variation between carbs (see attached pix-Carbs 1 & 2 on left, Carbs 3 & 4 on right.) The Mikuni spec indicates 3mm + or - 1mm which puts my fuel levels about right on.

However, in reading through the fuel level posts on this forum, it seems that the correct level of consensus is right at the lock washer on the float bowl screws. This gives a fuel level way below the Mikuni spec. Is this a fuel level that has been found empirically to work best on our bikes or am I just measuring incorrectly?

Any thoughts would be appreciated.

[Radioguylogs]

When I set my floats according to the FSM, the level is at the top of the lock washer when the bike is running.

I get erratic readings when the bike is not running.

In any case, your levels seem reasonable to me.

[DEEBS11]

Looks good!

[cajun31]

Are you having issues? Bike not running right? Leaks or flooding? If not then no worries.

[SouthernGrey64]

Thanks, Radioguylogs, Deebs, and Cajun31!
I am having trouble with the carburetors after installing new throttle shaft seals. # 3 cylinder won't fire. Too lean, suspect air leak somewhere. This will be the next test when I can get to it. I installed Suzuki seals, 13651-51011, which are supposed to be the same as Yamaha seals, 2A2-14997-00-00. I hope I got that right.
My inquiry above was because I have always been confused about the fuel level difference between the Mikuni spec and the float bowl lock washer height. And, before I Installed the carbs again, wanted to get some confirmation from the experts as to which was correct. I haven't had any leaks or flooding at the levels shown but the bike has been running rich.
Thanks again!

[jetmechmarty]

The float level and fuel level spec should amount to the same thing. If you set the floats to spec, theoretically the fuel level should be at the base of the mix chamber.
The XS650SH FSM says fuel level should be 1 +/-1 mm above the edge of the mix chamber. I expect XS1100 is the same, but I don’t have that manual right now.