mikuni fuel level

Anybody know what the fuel level should be in a Mikuni float bowl? I'v followed the float level instructions and fuel level is much lower in the float bowl than an amal.

Been a while since I did this and memory is a little hazy, but...

If I recall correctly, the Mik float is spring loaded with a very mild spring, if you're not aware of this, you lift the float PAST the springs closed point and think you are setting the level, whereas, actually, the float valve is closed when the spring touches. In other words, the float height is much lower than you thought.

I had a bike with the floats incorrectly set like this.

As per the Mikuni manual;

found at http://www.mikuni.com/pdf/vmmanual.pdf
It's good practice to roll the carb body ninety degrees clockwise from that drawing so that the float arm is pointing down, then roll the body back just a bit until the arm is in contact with the needle. That way, there's no ambiguity of how hard the arm might be pushing down on the needle to potentially compress the spring. This is then where you measure the arm tip.

This is what Fast Eddie is referring to when he says to not compress the spring inside the float needle. See carby-issues-are-clutch-t22739.html#p297944 for a run-down of my foibles two years ago along those same lines.

Nathan

I used this diagram to set the float level. I have the independent floats. The actual fuel level is way down in the bowl, a lot lower than amal and that is my question.

Assuming that your floats aren't fuel soaked or damaged, the correct float arm setting (for the 34mm VM Mikuni), with the carb upside-down, is parallel with the float bowel seating surface. As mentioned, the float needle spring should not be compressed while taking the measurement, which can be done by eye easy enough, and with only the float arm bearing on it, it probably won't compress, but it is easy enough to check: gently lift the float arm and then let it down slowly, if it compresses the spring then rotate the carb body until the spring doesn't compress; check for parallel. If the spring compresses you may need a new float needle. The spring is there to cushion the action of the needle against the seat.

If adjustment needs to be made, then gently bend the tab, on the float arm, that bears on the float needle with a small plain blade screwdriver. I recommend that you do not try to remove the float arm pivot, it is staked into a supporting structure, on one side with splines, and driving it out without proper support can cost you a carb. If you must remove the pivot, then you'll need an assistant or a specialized jig.

i second not removing the float arm pivot unless necessary. i broke off one of the float arm shaft support towers on a VM just tapping on a pin punch with the handle of a screwdriver. . .

seattle##gs said:

I used this diagram to set the float level. I have the independent floats. The actual fuel level is way down in the bowl, a lot lower than amal and that is my question.

Click to expand...

Keep in mind that the floats themselves make for a lot of volume in the bowl, so, once the two halves are separated, the fuel drops quite a bit from its actual running level. Are you having mixture issues while running?

Nathan

I am having some goofy problem of the motor kicking back every time I kick it. Everything checks out perfectly including the carb which was running just fine when delivered. I am now about to put a degree wheel on the crank to double check the timing mark on the alternator rotor. It seems like it is very retarded.
The battery is fully charged
black-white to black-white, black-yellow to black-yellow.
all grounds triple checked
The Boyer is static timed absolutely, positively on the money