I want to talk float heights

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radare
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Re: Let's talk float heights

Post by radare » Wed Jun 28, 2017 12:38 pm

cafe_bill wrote:
Wed Jun 28, 2017 11:42 am

Now it seems I need to open the bowls, give them some more height and go back to wet measurement... Sigh.
Let me know how your numbers come back when you do it. The 6-8mm bench setting should yield a wet height thats near the line, maybe 2 or so mm below it. I will be surprised if you don't come back with settings in the 12mm ballpark for bench setting to yield the 4-6mm fuel level mark.

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Re: Let's talk float heights

Post by radare » Fri Jun 30, 2017 12:01 pm

I'm going to propose that, instead of using float-height for setting carbs on the bench, that we use tab-height instead. Tab height correlates to float-height but takes the guess-work out of measuring from the gasket surface and deciding when the float valve is sufficiently compressed.

Tab Height, what is it?: The distance the float tab sits above the float body. Here's how it's measured:

Image

Image

Image

In this instance, the tab height is 0.228".


While setting the fuel levels, I took some measurements of tab height and compared that with the fuel level. There is an obvious trend that the higher the tab height, the lower the fuel level. Of course there is. That's how it works. But I wondered if there was a correlation that could be made between the two.

Using a set of carbs and taking a series of measurements, I found that, for this specific set of carbs, the two were related linearly within an adjustment band. So for the range of about 3mm to 7mm below the line, I found that the tab height changed based on this specific equation:

Tab Height = Fuel Level/(0.1537*Fuel Level)+0.1155)

Putting that into a table, I came up with the following:

Image

So what does that mean? Well, it means that, instead of shooting for a float height of 6-8mm above the gasket surface, the better approach might be to adjust tab height instead. With a tab-height of 0.224, I found I had a fuel level of 5mm below line and a float-height of roughly 12mm. This seems to agree with measurement's I've taken on stock-carbs that are still at the factory settings (of which, the float in the photos above is).

So here's my recommendation: Instead of using float height for initial carb setting, use tab height. Set the tab height according to your desired fuel level and then confirm fuel level on the bike.
Image
What do you guys think of this recommendation? I'd like for someone else, or a couple of someone elses to try it out and see if they get the same results before changing the float-height how-to.

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cafe_bill
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Re: Let's talk float heights

Post by cafe_bill » Wed Jul 05, 2017 6:00 pm

radare wrote:
Wed Jun 28, 2017 12:38 pm
cafe_bill wrote:
Wed Jun 28, 2017 11:42 am

Now it seems I need to open the bowls, give them some more height and go back to wet measurement... Sigh.
Let me know how your numbers come back when you do it. The 6-8mm bench setting should yield a wet height thats near the line, maybe 2 or so mm below it. I will be surprised if you don't come back with settings in the 12mm ballpark for bench setting to yield the 4-6mm fuel level mark.
Actually... With all four set dry at 8mm above the gasket surface, all four were between 4~6mm below the target line on the fuel bowl - amazingly close. After my third round of fill-check-drain-adjust, the wet levels are almost all equal and the dry version of measuring to the gasket surface shows a variation of a little less than 1mm on two of them. In the past I've not worried much if they were 4, 5 or 6mm below the line but rather to make sure all four are exactly the same.

Hopefully I'll have time to finish it all up next weekend and get the carbs back on the bike. Stay tuned...

FYI - the problem I had trying to start the bike turned out to be my own mistake reassembling the enrichment rail so sliding the knob only opened three of the four enrichment circuits.
Bill
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Michaelphilip
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Re: I want to talk float heights

Post by Michaelphilip » Fri Aug 04, 2017 4:36 pm

Maybe thats why i cant get mine to run right ever since i replaced all the parts in my carbs i have them set to the 6 to 8 now im going to go home and reset them and see what happens
You can run but you will just die tired

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