BritBike Forum logo
BritBike Sponsor BritBike Sponsor BritBike Sponsor
BritBike Sponsor

BritBike Sponsor

BritBike Sponsor
BritBike Sponsor BritBike Sponsor BritBike Sponsor
JWood Auction JRC Engineering dealers JWood Auction
Home | Sponsors, Newsletter | Regalia | Calendar | Bike Project | BritBike Museum | Spiders Cartoons, "OLD" BritBike Forum | DVD- Manuals & Parts books | BritBike Stickers & Decals
Upgrade to: Premium Membership | Premium Life Membership | Vendor Membership | Site Sponsor Membership
Photo posting tutorial

Member Spotlight
lincolntbird
lincolntbird
Caveside, Tasmania, Australia
Posts: 21
Joined: July 2013
Show All Member Profiles 
Shout Box
Search eBay for motorcycle parts in following countries
Australia, Canada, France, Holland, Italy, United Kingdom, USA
Random Gallery photo
Who's Online Now
192 registered members (68 royalstar tony), 1,662 guests, and 517 spiders.
Key: Admin, Global Mod, Mod
Newest Members
David Stothard, iansouthoz, Lightning Sim, Simon.Holyfield, Bushcreature
10036 Registered Users
Top Posters(30 Days)
Lannis 148
kommando 113
Stuart 61
Popular Topics(Views)
478,672 mail-order LSR
Forum Statistics
Forums33
Topics65,743
Posts635,554
Members10,036
Most Online3,995
Feb 13th, 2017
Like BritBike.com on Facebook

Previous Thread
Next Thread
Print Thread
Rate Thread
Concentric Float height #48211
07/11/06 11:40 pm
07/11/06 11:40 pm
Joined: Aug 2003
Posts: 74
Sydney, Australia
M
Mebbo Offline OP
BritBike Forum member
Mebbo  Offline OP
BritBike Forum member
M
Joined: Aug 2003
Posts: 74
Sydney, Australia
This is going to sound silly, but I really am having difficulty understanding certain operations of the AMAL Concentric - Mk1 anyway.

Reading lots of posts and instructions re the importance of float height to lean or rich running, I don't understand. From what I can see of the diagrams etc for Concentrics, the takeoff from the float chamber for both idle and open running is near the base of the chamber.

As long as the float needle is shutting off the intake to the chamber before the bowl floods into the carb moth (could it do that, or just pour out the tickler?), I would have thought it wouldn't matter what the float height was as long as enough fuel was available to the jets to sustain running.
The carb jets and manifold vacuum control how much fuel gets into the bore of the carb to mix with air, don't they? No more fuel can get into the mixing chamber than is allowed by those jets and the engine vaccum. Isn't the float chamber just a reservoir to provide sufficient fuel for the carb??
I could see that the if the float height were way too low, the carb might starve at full bore, but otherwise how can the fuel level in the chamber influence running?? How can the level affect the metering of fuel to the carb if the intakes are at the base and the jets/needle/vacuum control the flow?
Please educate, I'd love to know the answer!
Mebbo

Support Your #1 BritBike Forum!
Membership Type! Free
Member
Premium
Member
Premium Life
Member
Vendor
Member
Site
Sponsor
Recognition No Premium Member Premium Life member (5 years) Vendor Member Site Sponsor Membership
Post commercial threads No No No Yes Yes
Custom title No Yes Yes Yes Yes
Upload avatar & photos No Yes Yes Yes Yes
Link avatar & photos Yes Yes Yes Yes Yes
Private Message Storage: 10 100 100 100 100
Length of signatures 255 600 600 600 600
Removes this very advert island between post 1&2 No Yes Yes Yes Yes
Price Free $12.90/year $105.00 No End
$55.00/5 years
$210.00/year
($17.50/month)
Email
Click on button >>
  Premium Member Premium Life member Vendor Member Site Sponsor Membership
Re: Concentric Float height #48212
07/12/06 4:05 am
07/12/06 4:05 am

A
Anonymous
Unregistered
Anonymous
Unregistered
A


Too many thousand words required.
Try "venturi" and "head of pressure" in google.

Re: Concentric Float height #48213
07/12/06 6:42 am
07/12/06 6:42 am
Joined: Oct 2004
Posts: 4,429
Melbourne Australia
Tiger Offline
BritBike Forum member
Tiger  Offline
BritBike Forum member
Joined: Oct 2004
Posts: 4,429
Melbourne Australia
Think "suction lift".


1969 TR6R
7.62 x 51 is not a maths puzzle.
Re: Concentric Float height #48214
07/12/06 7:53 am
07/12/06 7:53 am
Joined: Aug 2003
Posts: 74
Sydney, Australia
M
Mebbo Offline OP
BritBike Forum member
Mebbo  Offline OP
BritBike Forum member
M
Joined: Aug 2003
Posts: 74
Sydney, Australia
Ahhh..Bernoulli's equation!
Thanks for the pointers.
That small height difference between the float level and the floor of the venturi can affect the flow velocity and therefore fuel volume from the outlet even if the venturi pressure drop is held constant.
the marvels of Google!

Mebbo
'70 Lightning
'74 850 Commando
'48 B32 (in bits)
'49 ZB34 Gold Star (in even more bits)

Re: Concentric Float height #48215
07/13/06 12:36 pm
07/13/06 12:36 pm
Joined: Oct 2003
Posts: 11,140
North Georgia, USA
RF Whatley Offline
BritBike Forum member
RF Whatley  Offline
BritBike Forum member
Joined: Oct 2003
Posts: 11,140
North Georgia, USA
Yea. Like they said.

If you were drinking burbon through one of those tiny, tiny straws, like a coffee stir stick, then believe me, you'd want to start with the liquid level near the top. Don't ask how I know this.


laughing


Don't hide 'em, Ride 'em !!

RF Whatley
Cornelia, GA

"Shop Boy" at Rodi British Bikes
Re: Concentric Float height #48216
07/13/06 11:39 pm
07/13/06 11:39 pm
Joined: Mar 2005
Posts: 10,024
Boston, Massachusetts
J
John Healy Online content
BritBike Forum member
John Healy  Online Content
BritBike Forum member
J
Joined: Mar 2005
Posts: 10,024
Boston, Massachusetts
Very simply put...
We are surrounded by air pressure. Approx 15 pounds per square inch at sea level. It is pushing on everything, including the gas in your float bowl.

Now you need a way to lift this gasoline into your inlet port. It won't go up there itself, even with the air presure pushing on it. But, create a vacuum in the inlet port and the differential in the air pressure (ambient air pressure pushing on tthe top of the gas in the bowl) vs. negative pressue in the port) and you can lift the gasoline up through the jets.

Remember that old saying: "Nature abhors a vacuum."
Well carburetros work on ambient air pressure, the air around us, and manifold vacuum. The higher the gasoline in the the less vacuum needed to lift it.

The higher the gas is in the bowl the less difference in pressure, or energy, required to lift the gasoline. As Panic suggests google venturi (venturis create vacuum).



Moderated by  Alan_nc 


Home | Sponsors | Newsletter | Regalia | Calendar | Bike Project | BritBike Museum | Spiders Cartoons | "OLD" BritBike Forum | DVD- Manuals & Parts books | BritBike Stickers & Decals
Upgrade to: Premium Membership | Premium Life Membership | Vendor Membership | Site Sponsor Membership
Powered by UBB.threads™ PHP Forum Software 7.6.1.1