Float Bowl Fuel Level

ericr · Post by **ericr** » 01:17 pm Mar 27 2018

I got my carbs back from RB Designs and opened them up to check the float level. I had read that the float height should be around 17-18 mm. They seem to be over 18, but I can't get an accurate measurement.

Using calipers, I can't touch the mounting surface and float at the same time - I can only eyeball it. I thought I could make a gauge that would sit flat on the mounting surface and then have something reach over the float at the right height.

How have others gotten accurate measurements? What have you set your float height to?

The shop manual lists 2 methods to set the fuel height; measuring the float height or measuring the fuel height with a bowl plug adapter and hose. The manual lists float height at 16mm +- 2. It lists fuel height as 0-2 mm above the float bowl mating surface. Has anyone done this? Would 0 mm from the mating surface be the same as a 18mm float height?

The reason I'm asking is that I went to ebay shopping for float height tools then found a used bowl drain plug for $9. I'm going to make my own fuel height gauge but am not sure what height to set it to.

Thanks!

John_S · Post by **John_S** » 02:07 pm Mar 27 2018

Heres what I use because I'm a craftsman

It works everytime just don't get it wet

ericr · Post by **ericr** » 03:03 pm Mar 27 2018

John_S wrote:Heres what I use because I'm a craftsman It works everytime just don't get it wet

I made one of those too out of cardboard but depending upon how I held it, my measurement was inconsistent. I needed a stable base, so this is what I came up with...

So, I take it that 18mm is the preferred level?

Post by **bufftester** » 12:16 am Mar 28 2018

I made one on the 3d printer that sits all the way across. Made them in several different sizes from 16-19 in 1 mm increments. Some people have better luck at 18 mm than 16mm, but as long as you are not having fuel dump out when the bike is sitting level you are ok. And yes, 18mm would be even with the float bowl mating surface.

ericr · Post by **ericr** » 12:35 am Mar 28 2018

bufftester wrote:I made one on the 3d printer that sits all the way across. Made them in several different sizes from 16-19 in 1 mm increments. Some people have better luck at 18 mm than 16mm, but as long as you are not having fuel dump out when the bike is sitting level you are ok. And yes, 18mm would be even with the float bowl mating surface.

Thanks, that's what I wanted to know. I've set my float height to 18mm, but I'm going to build a fuel height gauge too. We'll see how they correlate.

I've read so many threads about float height and learned that the height can affect the richness of the jetting. For RB Design modded carbs, is 18mm the optimal height for tuning and reaching SSS nirvana?

kdxdazz · Post by **kdxdazz** » 02:33 am Mar 28 2018

i had to use the clear tube method to get it level with the fuel bowl mating surface,my float height had to be set at 21mm

BamBam · Post by **BamBam** » 10:42 am Apr 17 2018

Making a gauge seems like a good idea... and this is measuring up to the plastic peak (highest point) on the bottom of float, correct?

John_S · Post by **John_S** » 12:53 pm Apr 17 2018

BamBam wrote:Making a gauge seems like a good idea... and this is measuring up to the plastic peak (highest point) on the bottom of float, correct?

Correct

Post by **SS109** » 03:09 pm Apr 17 2018

My cheap one made from an Uber business carb. Works great!

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