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Amal 276 questions #725132
02/11/18 3:16 am
02/11/18 3:16 am
Joined: Dec 2014
Posts: 138
Perth, Western Australia
H
Howley Offline OP
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Howley  Offline OP
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Joined: Dec 2014
Posts: 138
Perth, Western Australia
Hi,

I have three questions:

1. The literature states the m21 uses a "standard" needle jet. What size is that. 0.106?

2. How do I tell if my throttle slide/body is worn?

3. Are there any baseline settings for the pilot air screw?

This is on a 1949 m21.

Thanks!

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Re: Amal 276 questions [Re: Howley] #725144
02/11/18 5:14 am
02/11/18 5:14 am
Joined: Aug 2016
Posts: 42
Canterbury, New Zealand
B
BevanC Offline
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BevanC  Offline
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Joined: Aug 2016
Posts: 42
Canterbury, New Zealand
Gidday,
You probably kniw this already, but Draganfly.co.uk have a comprehensive listing of carb data for BSA models, including M21.
Cheers, Bevan

Re: Amal 276 questions [Re: Howley] #725145
02/11/18 5:30 am
02/11/18 5:30 am
Joined: Dec 2014
Posts: 138
Perth, Western Australia
H
Howley Offline OP
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Howley  Offline OP
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Joined: Dec 2014
Posts: 138
Perth, Western Australia
Yep, I've seen it. It just lists 'std' for the m21.

Re: Amal 276 questions [Re: Howley] #725149
02/11/18 8:43 am
02/11/18 8:43 am
Joined: Sep 2008
Posts: 133
United kingdom
P
Phil Beresford Offline
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Phil Beresford  Offline
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Joined: Sep 2008
Posts: 133
United kingdom
The "standard" needle jet size on 276 carburettors was .1065".

Re: Amal 276 questions [Re: Howley] #725150
02/11/18 9:00 am
02/11/18 9:00 am
Joined: Oct 2001
Posts: 1,150
Sydney, Oz
S
Shane in Oz Offline
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Shane in Oz  Offline
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Sydney, Oz
Amal has a nice little search capability fo finding the right carb for specific models, though it can take a few attempts to narrow down.

Once you have the right carb, go down to the parts lit and click on "view" for the carburettor. It shows the M21 has a 276BR/1B, with a 4 slide, 160 main and 106 needle jet.

Re: Amal 276 questions [Re: Howley] #725162
02/11/18 10:54 am
02/11/18 10:54 am
Joined: Dec 2014
Posts: 138
Perth, Western Australia
H
Howley Offline OP
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Howley  Offline OP
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Joined: Dec 2014
Posts: 138
Perth, Western Australia
Thanks guys.

Buried in the bsa parts book it list a 0.1065 needle as Phil said.
Thanks Shane, I didn't know about that feature on the website.

Having disassembled the carb I found the needle clip missing, a worn, pitted and bent needle on the wrong position and a 130 main jet. No wonder it was hard to start!

Re: Amal 276 questions [Re: Howley] #725181
02/11/18 1:05 pm
02/11/18 1:05 pm
Joined: Aug 2001
Posts: 3,987
argyll. scotland, uk
gavin eisler Online content
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gavin eisler  Online Content
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argyll. scotland, uk
If the bike is running and you push the slide towards the motor with a finger and the engine note changes, the slide is worn out, they are about a 3 thou loose fit when new. Really bad slides will rattle at tickover.


71 Devimead A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
Re: Amal 276 questions [Re: Howley] #725187
02/11/18 2:49 pm
02/11/18 2:49 pm
Joined: Aug 2015
Posts: 1,196
Bolton Lancs UK
A
Andy Higham Online content
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Andy Higham  Online Content
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Posts: 1,196
Bolton Lancs UK
You would be very lucky indeed to find a Concentric with 0.003" clearance even when new


1955 BSA B31 500cc "Stargazer"
1962 Greeves 200cc "Blue Meanie"
1962/67 Greeves 350
1967 Greeves 360 Challenger
1984 Suzuki GSX1100 EFE "Sorcerers Apprentice"
GM500cc sprint/LSR bike "Deofol"
Jawa 500cc "Llareggub"
2003 Aprilia RSV Mille "Lo Stregone"
Re: Amal 276 questions [Re: Howley] #725189
02/11/18 2:59 pm
02/11/18 2:59 pm
Joined: Aug 2001
Posts: 3,987
argyll. scotland, uk
gavin eisler Online content
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gavin eisler  Online Content
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Posts: 3,987
argyll. scotland, uk
Talking slide fit, a mate with a lathe made new slides for his concs, , much tighter fit, more like 0.001", the bike wouldnt run at all, I loaned him an old set and it ran fine, they were designed for a loose fit. Once they are truly Donald ducked the tickover goes unstable, by then you can hear them rattling.


71 Devimead A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
Re: Amal 276 questions [Re: Howley] #725190
02/11/18 3:02 pm
02/11/18 3:02 pm
Joined: Mar 2005
Posts: 10,172
Boston, Massachusetts
J
John Healy Online content
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John Healy  Online Content
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Joined: Mar 2005
Posts: 10,172
Boston, Massachusetts
Quote
You would be very lucky indeed to find a Concentric with 0.003" clearance even when new


And for very valid reasons!!!!

When the clearance was increased by AMAL, modifications were made to the low throttle jetting specification to compensate. When a Concentric is sleeved, and the slide clearance is reduced below the correct clearance, the jetting at low throttle openings will be very rich. Boring the body to "clean-it-up" weakens the structural integrity of the body and actually increases the chances that the slide will stick when the mounting hardware is over tightened. When AMAL decided upon the slide clearance they new what they were doing!


Re: Amal 276 questions [Re: Howley] #726950
02/27/18 12:33 pm
02/27/18 12:33 pm
Joined: Dec 2014
Posts: 138
Perth, Western Australia
H
Howley Offline OP
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Howley  Offline OP
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Joined: Dec 2014
Posts: 138
Perth, Western Australia
Hi guys.

Update. I got some new bits, including a new slide since the old one was totally cooked.
Weirdly, the new slide is basically a 'press fit' in the bore. It's a tight slip fit in the upper section and very tight toward the intake.
Obviously it's not going to function as is, is it safe to skim the bore to bring it out to the 0.003" clearance?
I'd hone it if my hone would fit inside...

Any thoughts?

Re: Amal 276 questions [Re: Howley] #726964
02/27/18 2:39 pm
02/27/18 2:39 pm
Joined: Feb 2007
Posts: 613
Ewing. NJ
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edunham Offline
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Posts: 613
Ewing. NJ
Either the new slide is oversize, or more likely your carb body is warped. I would check for warping, and if present, try to remedy that through careful use of pressure rather than boring.

Ed from NJ

Re: Amal 276 questions [Re: Howley] #727495
03/04/18 1:40 pm
03/04/18 1:40 pm
Joined: Dec 2014
Posts: 138
Perth, Western Australia
H
Howley Offline OP
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Howley  Offline OP
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Joined: Dec 2014
Posts: 138
Perth, Western Australia
Good call mate. A bit of work in the vise and a light hone did the job.


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