Preaching On Fuel Level Set-Up

Guys, I must say I learned a valuable lesson in the last few days. I thought I knew carburettors - after all, I've been restoring and tuning for 30 years. This is my first 4 stroke Kawasaki, a 1976 KZ900. I bought it from an EBay auction that failed to meet the reserve in late Feb.

I have never used a fuel level method of setting carbs. I have done 100's of them and had great success with setting "float height". I took these apart the week I bough tthe bike and started restoring the filtering system - snorkle and all, replacing the needles and jets with factory sizes and pieces along with a new set of Doremi 4/4 repro pipes. What is different though, these KZ carbs are my first with composite material floats. These floats were set up "exactly" at 26mm float height.

I rode the bikes for weeks and just never could get it to idle correctly, the idle mixture never had much impact, and the plugs kept reading "way rich" at low speeds. As soon as the throttle was opened, the bike ran perfectly.

The problem? Fuel levels too high in 3 of the 4 carburettors. I checked the the fuel levels when the new gauge arrived and 3 of the 4 were actually above the top of the bowl body- same float height on all 4, but the floats had lost bouyancy! Even though I had new, factory seats and valve assemblies - with the reduced bouyancy, the floats were not shutting fuel off before it was sloshing over into the intake tract. This was 100% of the problem.

For those who say level does not matter - you're lucky. The differences in fuel level and what it took to get the 4mm below bowl top level was not the same on any of the floats - none had the same bouyancy. All the carbs I'd had good luck with before were copper - not composite. These composite floats do differ and I will always believe change over time. Fuel level set-up is the only way to get it right.

Regards,Gordon

Absolutely !
You're right on the money there Ibikes. When I had a cylinder running rich and could'nt figure out why it was because I had too high a fuel level in that carb. A simple adjustment made all the diifference.

On my 750 twin, when one fuel level was about 1mm higher than the other, it never idled smooth and I could hear the popping on decel. They do need to be equal since the fuel level feeds the whole system.

del

JMKZHI wrote:

...So I laboriously did 'em all over again using a fuel level gauge....

If not already doing so, a good time-saving tip (learned from wiredgeorge) is using only one of the four float bowl screws during the fuel level testing. Because any slight gasket seepage doesn't affect readings in the plastic tube.

Good Luck!

del

Got a pic of the homemade carb stand?

Mine was a 1 X 8 in the vise, with two manifolds screwed to the board. This let's you set the levels on the bench instead of on the bike