How many " Hg on a Bing carb

rustygardhouse · 09-02-2012, 04:01 AM

Here's a great geeky question for the airhead carb synchers; there 's some very fancy rigs out there:

Anyone know how many (pick a pressure unit of your choice) a Bing carb pulls at 4000 rpm?

Is there a difference between 32s & 40s?

Anyone else want to list their carb & rpm?

thx

R

pthomas · 09-02-2012, 06:20 AM

It depends on the weather but I don't know how much difference there is from the outside pressure.

ritetwist · 09-02-2012, 07:30 AM

Having just read your post and to satisfy my own curiosity, I got a 3" face needle style vacuum gauge from my misc. box of instrumentation type "stuff".Only thing is that it reads in centimeters of Hg.Max. of 76 cm. scale.
At idle it reads 13 cm.4,200 rpm reading is at 11 cm.vacuum.
For a rough comparison, I can suck 20 cm. by mouth.(no jokes).
Bike is a '95 GSPD with 40 mm carbs.
13 cm.would be roughly 5.1".

rustygardhouse · 09-05-2012, 01:27 AM

Wow! I thought this would be a post-a-thon! I know this subject sucks (sorry) but I expected more.

Thanks for actually measuring the vacuum; it gives me a good starting point.

ritetwist · 09-05-2012, 07:24 AM

I also checked my '82 r65ls (32 mm carbs).@ 4000 showed 12 cm.
I don't know what you are using these findings for.To some extent they may show engine condition,perhaps
air filter condition.But to what end?
More important is checking that both carbs are the same,part of your idle setting.
I did not get to mussing with the idle mix to see if that changed the vacuum reading.

rustygardhouse · 09-13-2012, 04:43 PM

Well, it's sort of this way...

I like the Harmonizer but can't get one. Being a design engineer, I started to look at how this & the Twinmax work to see if I could build my own.

I'm a mech so I started to talk to an elec friend of mine to help with the circuit.

To pick the right sensor we needed to know how much vacuum is being pulled. I could make up a water manometer & risk hydraulicing my cylinders.

Or I could ask the forum!

09-02-2012, 04:01 AM	#1
rustygardhouse ^OP rusty Joined: Jun 2012 Oddometer: 30	How many " Hg on a Bing carb Here's a great geeky question for the airhead carb synchers; there 's some very fancy rigs out there: Anyone know how many (pick a pressure unit of your choice) a Bing carb pulls at 4000 rpm? Is there a difference between 32s & 40s? Anyone else want to list their carb & rpm? thx R

09-02-2012, 06:20 AM	#2
pthomas Gnarly Adventurer Joined: Jan 2011 Location: St. Petersburg, FL Oddometer: 180	It depends on the weather but I don't know how much difference there is from the outside pressure. __________________ Paul 1974 R90/6

09-02-2012, 07:30 AM	#3
ritetwist Gnarly Adventurer Joined: Jun 2011 Location: North AB, CDA Oddometer: 120	Having just read your post and to satisfy my own curiosity, I got a 3" face needle style vacuum gauge from my misc. box of instrumentation type "stuff".Only thing is that it reads in centimeters of Hg.Max. of 76 cm. scale. At idle it reads 13 cm.4,200 rpm reading is at 11 cm.vacuum. For a rough comparison, I can suck 20 cm. by mouth.(no jokes). Bike is a '95 GSPD with 40 mm carbs. 13 cm.would be roughly 5.1". __________________ Afraid to sleep for fear of missing something.

09-05-2012, 07:24 AM	#5
ritetwist Gnarly Adventurer Joined: Jun 2011 Location: North AB, CDA Oddometer: 120	I also checked my '82 r65ls (32 mm carbs).@ 4000 showed 12 cm. I don't know what you are using these findings for.To some extent they may show engine condition,perhaps air filter condition.But to what end? More important is checking that both carbs are the same,part of your idle setting. I did not get to mussing with the idle mix to see if that changed the vacuum reading. __________________ Afraid to sleep for fear of missing something.

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09-05-2012, 01:27 AM	#4
rustygardhouse ^OP rusty Joined: Jun 2012 Oddometer: 30	Wow! I thought this would be a post-a-thon! I know this subject sucks (sorry) but I expected more. Thanks for actually measuring the vacuum; it gives me a good starting point.

09-13-2012, 04:43 PM	#6
rustygardhouse ^OP rusty Joined: Jun 2012 Oddometer: 30	Well, it's sort of this way... I like the Harmonizer but can't get one. Being a design engineer, I started to look at how this & the Twinmax work to see if I could build my own. I'm a mech so I started to talk to an elec friend of mine to help with the circuit. To pick the right sensor we needed to know how much vacuum is being pulled. I could make up a water manometer & risk hydraulicing my cylinders. Or I could ask the forum!