Author Topic: PHF30 float level adjustment  (Read 286 times)

Offline brider

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PHF30 float level adjustment
« on: March 26, 2019, 08:54:48 PM »
OK, now that I have a path forward on my air filters, I need some guidance on my PHF30 carb float-height adjustment (or not).

I was following the guidance of Greg's teachings, plus some other entries here:

http://www.thisoldtractor.com/dellorto_setting_the_float_height_on__carburetors.html

The guidance in Fig 13 of the link does not state this, but I assume the float should be flopped over until it JUST closes the needle valve. The problem I'm having is it's IMPOSSIBLE to determine when this is with the tiny, tiny spring rate on that tiny, tiny spring.

The VHB carbs specify a more typical method, with the carbs upside-down and the float compressing the spring to a calibrated amount.

If I use this upside-down method, the float compresses the spring COMPLETELY, bottoms it out, and the height measures below the specified 18 mm (.709 in).

If I use the Fig 13 method, there is no way I can sense when the needle valve actually makes contact in order to measure the height. One previous poster said to use a small hole attached to that circuit and blow thru it to see when the valve closes. But I still have the problem of holding the float dead-still when that happens and measuring, which seems full of error.

The GOOD thing is the bike WAS running/burning perfectly before I dismantled it, so should I even bother, and just leave well-enough alone?
'85 Cal II Auto
'86 LM IV (sold)
'71 Ambo project
Wish'd I'd never sold:
'72 Red Eldo
'74 White Eldo LAPD
'77 Convert with DB bags
'06 Gas Gas EC300

Online Chuck in Indiana

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Re: PHF30 float level adjustment
« Reply #1 on: March 27, 2019, 08:11:53 AM »
Turn the carb upside down and eyeball the split line of the float. Parallel to the carb body? Close enough. If it closes too soon, the carb will eventually run out of fuel on a long WFO run. If it closes too late, it will run rich.
Chuck in (Elwood) Indiana/sometimes SoCal

02 Scura RC
87 AeroLario
79 G5
95 Skorpion tour
 
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Offline brider

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Re: PHF30 float level adjustment
« Reply #2 on: March 27, 2019, 10:13:10 AM »
Turn the carb upside down and eyeball the split line of the float. Parallel to the carb body? Close enough.

I ain't so sure this is going to work, although I understand the logic and your point.

As I mentioned, when I turn the carb upside-down, the float compresses the spring COMPLETELY as it is now, and the split-line is BELOW level. If I were to adjust so the split-line IS level, I'd be closing the circuit early. My problem is I can't tell, due to the softness of the spring, just WHEN the valve closes, which is really where you want the split-line to be level.

I may think thru this some more, but then just put it back together. Don't want to "fix" what ain't broken.
'85 Cal II Auto
'86 LM IV (sold)
'71 Ambo project
Wish'd I'd never sold:
'72 Red Eldo
'74 White Eldo LAPD
'77 Convert with DB bags
'06 Gas Gas EC300

Online wirespokes

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Re: PHF30 float level adjustment
« Reply #3 on: March 27, 2019, 03:20:58 PM »
I haven't done this with the Dells that I recall, but lots of times with Bings. A float is a float - not a whole lot of difference in the way they operate. In this case, they both specify float casting line parallel to the carb. Here's how I've done it: With the float bowl off (carb still attached, fuel off), hold the float up to stop fuel flow. Open petcock and slowly lower the float noting where the fuel flows. Then push the float back up and note where it turns back off. Eyeball the casting lines for parallel - adjust as needed.

Offline brider

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Re: PHF30 float level adjustment
« Reply #4 on: March 28, 2019, 06:45:51 PM »
With the float bowl off (carb still attached, fuel off), hold the float up to stop fuel flow. Open petcock and slowly lower the float noting where the fuel flows. Then push the float back up and note where it turns back off. Eyeball the casting lines for parallel - adjust as needed.

Makes perfect sense, thanks!
'85 Cal II Auto
'86 LM IV (sold)
'71 Ambo project
Wish'd I'd never sold:
'72 Red Eldo
'74 White Eldo LAPD
'77 Convert with DB bags
'06 Gas Gas EC300

 

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