Originally Posted by polex
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II measured the bowl fuel float level by following the procedure indicated in Service Manual.
This way for measuring can be followed without disassemble the carburetor. The gasoline level is 3-5 mm. below Joint face... The specification is 1.5 mm. above joint face. I noticed that in "proven setups" the bowl fuel float level is measured in different way.
Is the 17.5 mm the OEM height ?
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The Service manual check is a go/nogo test and impossibly tedious to use as a means of setting the float heights.
Haynes gives a 14.5mm float height figure for both the Mikuni and Keihin carbs and the 17.5mm figure is from Factory Pro and for use with the FP needles.
Triumph gives no float height measurement but allows a pretty large variance in fuel depth with their 1.5mm +/- 1mm value, so the difference between Haynes and FP seems pretty reasonable overall.
So... I'd say that if you're using the stock needles and jetting then use the Haynes 14.5mm float height setting. You can always adjust it later toward the FP 17.5mm setting if the bike is too rich throughout the operating range. (Raising the float height lowers the fuel level in the bowls and leans out the mixture.)
To adjust the float height, remove the carbs from the bike and the float bowls from the carbs. Lay them on your workbench with the float pivots up and the bowl mating surfaces vertical. Gradually roatate them until the float height adjustment tabs just touch the float valve spring pins without compressing them. (There's a small spring-loaded pin in each of the float needle valves.)
Measure from the bowl mating surface to the highest point on the floats. You must be careful to keep your ruler square to the mating surface. Any tilt of the ruler will give you an erroneous setting.
If adjustment is requred, gently push out the float pivot pin with a paper clip or similar and bend the adjustment tab by pressing it against a hard obect. (I use the corner of a wooden block and finger pressure only.)
A tiny change in the bend of the adjustment tab will produce a large change in float height, so take it easy! DO NOT use pliers or screwdriver leverage to bend the tab. These things are delicate!
After bending the tab, replace the float in the carb, re-insert the pivot pin and check the measurement.
On the road you'll find out if your float adjustments are accurate when you hit the reserve on the fuel tank. If all three floats are set identically the engine will shut down like somebody flipped a switch. If the engine shuts down one cylinder at a time then the float heights are a bit off.
Leaving them a bit off is much less scary.
It's not a difficult process but it's exacting and delicate.
Jim
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