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Preaching On Fuel Level Set-Up
- Ilbikes
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13 May 2008 18:13 #213407
by Ilbikes
Preaching On Fuel Level Set-Up was created by Ilbikes
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
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
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- JR
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13 May 2008 18:21 #213408
by JR
1980 kz750E1, Delkevic exhaust
Replied by JR on topic Preaching On Fuel Level Set-Up
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.
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.
1980 kz750E1, Delkevic exhaust
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- bountyhunter
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13 May 2008 19:43 #213436
by bountyhunter
1979 KZ-750 Twin
Replied by bountyhunter on topic Preaching On Fuel Level Set-Up
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.
1979 KZ-750 Twin
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- JMKZHI
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14 May 2008 05:00 - 04 Dec 2008 06:11 #213505
by JMKZHI
Replied by JMKZHI on topic .
del
Last edit: 04 Dec 2008 06:11 by JMKZHI.
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- Patton
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14 May 2008 05:39 #213508
by Patton
1973 Z1
KZ900 LTD
Replied by Patton on topic Preaching On Fuel Level Set-Up
JMKZHI wrote:
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!
...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!
1973 Z1
KZ900 LTD
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- JMKZHI
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14 May 2008 05:55 - 04 Dec 2008 06:28 #213511
by JMKZHI
Replied by JMKZHI on topic .
del
Last edit: 04 Dec 2008 06:28 by JMKZHI.
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14 May 2008 10:23 #213553
by OKC_Kent
Oklahoma City, OK
78 KZ650 B2 82,000+ miles
Replied by OKC_Kent on topic Preaching On Fuel Level Set-Up
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
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
Oklahoma City, OK
78 KZ650 B2 82,000+ miles
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