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Re: Tuning Your AMAL Carburetor [Re: Morgan aka Admin] #564425 09/22/14 5:22 am
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Allan Gill Offline
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Before you start straightening the carb, check the body for wear and gauling. If it's bad I wouldn't waste time in straightening the body.


beerchug
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Re: Tuning Your AMAL Carburetor [Re: Morgan aka Admin] #567844 10/15/14 9:36 pm
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57BSA Offline
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Can someone please help with AMAL Carb, I want to order a new AMAL for my 57 A10. No markings on outside but the slide says 376/3. How can I find out what carb is suppose to be on it and if needed jet size, etc.

Re: Tuning Your AMAL Carburetor [Re: Morgan aka Admin] #567912 10/16/14 10:41 am
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Alex Offline
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A smattering:
'53 Gold Flash
'67 Royal Star
'71 Rickman Metisse
'40 Silver Star
'37 Rudge Special
sixtyseventy Lightboltrocket road racer...and many more.
Re: Tuning Your AMAL Carburetor [Re: Morgan aka Admin] #574389 11/29/14 3:22 pm
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Irish Swede Offline
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Regarding flange warpage: I checked seven Monobloc bodies this morning. Only one had a mounting flange that was still flat.

Although this is frequently seen in Concentric Amals, it appears ALL AMAL carb bodies should be checked for this condition.

I recall that a Britbike site participant had designed and made a jig to straighten the mounting flanges by use of a round bar inserted through the carburetor body, top-to-bottom.

Does anyone have drawings and measurements for this item?

Re: Tuning Your AMAL Carburetor [Re: Irish Swede] #574395 11/29/14 4:34 pm
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Magnetoman Online Content
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Originally Posted by Irish Swede
Does anyone have drawings and measurements for this item?
Take a look at the following post as well as the one two posts below it in the same thread:

http://www.britbike.com/forums/ubbthreads.php?ubb=showflat&Number=571680#Post571680

Re: Tuning Your AMAL Carburetor [Re: Morgan aka Admin] #574426 11/29/14 9:25 pm
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Irish Swede Offline
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Thank you. That is what I am looking for.

Re: Tuning Your AMAL Carburetor [Re: Morgan aka Admin] #574444 11/29/14 10:57 pm
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John Healy Offline
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Quote
I recall that a Britbike site participant had designed and made a jig to straighten the mounting flanges by use of a round bar inserted through the carburetor body, top-to-bottom.


http://www.britbike.com/forums/ubbthreads.php?ubb=showflat&Number=220880

You need a different plug for each 376, 389, 600 and 900 series bodies. The plug needs to be approx. .005" pr so smaller than the diameter of the slide. The plug needs to be cut just like the bottom of a slide so it engages the full length of the slide cavity in the body. The rest should be self explanatory. This is something that has been done for years. Look at the date on the letter from Mike Gaylord 1994.


Re: Tuning Your AMAL Carburetor [Re: John Healy] #574449 11/30/14 12:24 am
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Magnetoman Online Content
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Originally Posted by John Healy
plug needs to be cut just like the bottom of a slide so it engages the full length of the slide cavity in the body.
Or the jet block needs to be removed if you want to use a solid rod all the way to the bottom of the bore as I do. If I were doing lots of them I'd certainly hollow out the bottom as John suggests to make the job faster, but a solid rod has the advantage of not being subject to (possible) distortion. It may well be that distortion of the bottom of the rod is a needless concern, but I only do one carburetor every blue moon so I don't have to worry about production efficiency.

Re: Tuning Your AMAL Carburetor [Re: Morgan aka Admin] #574516 11/30/14 3:07 pm
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Irish Swede Offline
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Again, thanks, Magnetoman and John.

This additional information will go into my files on Monobloc and Concentric repair and tuning.
I have several of each type of carb that need sleeving and rebuilding. I need to see if I can
straighten the mounting flange of each before I send it for the "sleeve job."

I have owned and ridden Triumphs since 1967, but was unaware of how little I knew about AMAL carbs
until I discovered the BRITBIKE website.


Re: Tuning Your AMAL Carburetor [Re: Morgan aka Admin] #575485 12/07/14 9:54 pm
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I have scanned this thread trying to figure out what main jet size I should be using in my current A65 project, but I think I lack the background understanding to sort this out so maybe some of you nice folks can help me. I have a 1967 A65 Lightning that I just converted to single carb. I have at my disposal either a 389 Monobloc or a 932 Concentric. (Actually have a pair of each) For starters I am planning on using the Monobloc, since I am more familiar with them because I have one on my 66 Thunderbird. (I am willing to listen if someone has strong opinions as to why this is a bad idea) I am running straight pipes, which are the stock ones that have been extended by about 15" and have 12" baffles installed; (metal baffles, no glass). The 389 I have has a size 270 main jet in it, and I believe the Concentrics do as well. It seems that that's what they put in the dual carbs. Stock jet for the Thunderbolt (single carb) is 230. With my exhaust set up I would imagine I should use a slightly larger jet???. (compared to the 230) But how much larger? Thanks to all who can help educate me/point me in the right direction!
-Dave


vdog
66 6T
67 A65L
72 T100R
Re: Tuning Your AMAL Carburetor [Re: Morgan aka Admin] #575496 12/08/14 12:00 am
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Great, thanks Nick. That's what I was looking for, sort of a jumping off point.


vdog
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72 T100R
Re: Tuning Your AMAL Carburetor [Re: Morgan aka Admin] #575624 12/08/14 9:58 pm
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James captain Offline
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Thanks mate, I'm into the early British stuff particularly & have just started a resto on a James Captain deluxe that I've had for years. 99% there just missing the side stand & front guard embellisher at this early stage - watch this space, we all know how this can blow out. Anyhoo obviously parts & sources are pretty limited here in Aus. so I was hoping to track down stuff with the help of an online forum & the vast combined knowledge that's out there. Never used a forum before haven't really got a clue just fumbling through for now, bear with me. Look forward to any feedback regarding James stuff, done all the cyber surfing got a little bit of info but not much regarding parts.

Re: Tuning Your AMAL Carburetor [Re: James captain] #575766 12/09/14 11:39 pm
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Vetterdog Offline
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Originally Posted by James captain
Thanks mate, I'm into the early British stuff particularly & have just started a resto on a James Captain deluxe that I've had for years. 99% there just missing the side stand & front guard embellisher at this early stage - watch this space, we all know how this can blow out. Anyhoo obviously parts & sources are pretty limited here in Aus. so I was hoping to track down stuff with the help of an online forum & the vast combined knowledge that's out there. Never used a forum before haven't really got a clue just fumbling through for now, bear with me. Look forward to any feedback regarding James stuff, done all the cyber surfing got a little bit of info but not much regarding parts.


I think we're gonna need to see some pictures of that!


vdog
66 6T
67 A65L
72 T100R
Re: Tuning Your AMAL Carburetor [Re: Morgan aka Admin] #575825 12/10/14 4:51 pm
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Greetings, all!
Anyone have a source for Monobloc float cover screws already drilled for safety-wire? Stainless screws would be additionally nice. I've a couple of carbs that came with saftey-wired screws that appear to be factory drilled items. The head protrudes a bit "proud' to allow for drilling. Nice looking set up, just a bit rusty..... Any suggestions?

Thanks!

Bigtwin

Re: Tuning Your AMAL Carburetor [Re: Morgan aka Admin] #575989 12/12/14 6:34 am
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Phil Beresford Offline
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Get them from AMAL or one of their dealers.

http://amalcarb.co.uk/monobloc-wired-screw-kit.html

Re: Tuning Your AMAL Carburetor [Re: Morgan aka Admin] #623986 11/02/15 4:03 am
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Allan Gill Offline
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Which main jet holder do you have fitted? There are two types, the two stroke type which is like a bolt, and the 4stroke type which is fluted on the main jet side of the nut, putting the main jet lower in the fuel and further away from the needle.


beerchug
Re: Tuning Your AMAL Carburetor [Re: Morgan aka Admin] #624004 11/02/15 10:04 am
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John Healy Offline
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You arrive to do some work and you read:
Quote
Did you know...
The 928/104 4-ring needle originally/currently fitted to AMAL Mk1s on the 850 Norton Commando is so overlength by design that it interferes with the main jet unless the clip is set at the bottom (richest) position.


Well Owen, I thought I had heard everything. So I had to get out my cutaway Concentric I use for seminars just to see what you are talking about. No, the needle doesn't hit the main jet in any one of the three clip positions. I fact there is about 1/8" clearance when the clip is in the top position.

Several things come to mind: As mentioned in another thread the carb is fitted with a 2 stroke main jet holder which is shorter than the 4 stroke version. Or the needle you are using was not made to the drawing. This is entirely possible as there are a lot of people trying to copy AMAL parts all over the world. Most don't work as the original.


Re: Tuning Your AMAL Carburetor [Re: ] #624043 11/02/15 5:29 pm
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Originally Posted by needing
Oops. Sorry Allen but I assumed people knew Norton Commandos are 4 stroke. I posted in this general thread 'Tuning Your AMAL Carb...' to advise anyone considering/actually using 'long' needles to delay the 'taper start' that the extra length comes with a penalty. Shimming the main jet lower could be a possible solution as is cutting the end off the needle.
I know almost nothing of and care less for twostrokes e.g. Bantams.
Ta.
Owen.


Not the point I was making ( but I'm glad John read the piece with an open mind. )

Best thing you can do is this

Remove the float bowl and post a picture of what you have showing the main jet in situ.

Remove the needle and measure it's full length.

I will find the data AMAL provide for these carbs. I can say with great confidence that AMAL wouldn't send out a carb with problems like this.


beerchug
Re: Tuning Your AMAL Carburetor [Re: Morgan aka Admin] #624046 11/02/15 6:07 pm
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Allan Gill Offline
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http://amalcarb.co.uk/rebuilding-mark-1-concentric-carburetter

Scroll down to the bit with main jets and especially main jet holders, below is about needles but I couldn't find info about needle length.

I would also strongly recommend reading the whole article, if you don't know about the jet holder then there is probably very little you do know or accurately knew a small amount of what you had been taught.

To add, yes your commando is a 4 stroke, it's probably the most well known classic bike around besides the Goldstar and the bonneville.


beerchug
Re: Tuning Your AMAL Carburetor [Re: Morgan aka Admin] #626532 11/20/15 5:18 pm
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Rohan Offline
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Doesn't the AMAL manual say that 850 needles should only be fitted to 850 stepped spray tube needle jet setups ??

Re: Tuning Your AMAL Carburetor [Re: Morgan aka Admin] #626546 11/20/15 7:03 pm
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John Healy Offline
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I have never seen that information. The 928/104 will lean out the mixture at mid to 3/4 throttle.


Re: Tuning Your AMAL Carburetor [Re: Morgan aka Admin] #626559 11/20/15 7:58 pm
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John Healy Offline
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So I am confused: here are two pictures of a 928/104 needle with the clip in the top groove. The needle came out of a AMAL bag and is from current production. I took a current production main jet out of an AMAL bag and cut a portion of it away so we could see the needle.

The slide is set as it would be if the bike was idling. That is with the back edge .015" off the bottom of the venturi. There is no way this needle blocks the main jet.

[Linked Image]

[Linked Image]

The needle measures from the bottom edge of the top groove to the tip of the needle 2.560" - give or take a thousandth.

What is it that I am not seeing?


Re: Tuning Your AMAL Carburetor [Re: John Healy] #626579 11/20/15 9:27 pm
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Rohan Offline
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Originally Posted by John Healy
I have never seen that information.


The 4 ring needles are 1/4" longer,
according to all the old chat on this...

Re: Tuning Your AMAL Carburetor [Re: Morgan aka Admin] #626607 11/21/15 12:18 am
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John Healy Offline
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OK, the 928/104 is 0.088" longer than the 622/124 not 1/4" longer.

When sans clip and dropped through the slide fully seated in the body the 928/104 needle drops, and stops against the bottom of the main jet, with the top of the needle a few thousandths above the clip seating on the top of the slide. This means it has at least 0.100" clearance when the clip is installed. When the carburetor set up to run, and idle, the tip of the needle will never block the main jet, or bang against it in any way.

To set the slide at an average idle opening of 0.015" it only takes 3/4 of a turn of the throttle stop screw. This gives gives at least an 1/8" clearance between tip of needle and the orifice of the main jet with the slide seated in the body. Even with the needle clip in the top notch and the carburetor adjusted so it will idle the 928/124 needle will not block the main jet in any way.

With a carburetor with proper slide clearance the engine will die if the slide is lowered so the back edge of the slide is below the bottom of the venturi. In that video the air to allow it to idle isn't being supplied through transfer port which I think you are suggesting

Yes, air passes through the larger of the two transfer ports into the mixing chamber below at idle speeds. This is because the differences in pressure on each side of the slide. As the slide is lifted, and manifold vacuum balances the larger port now becomes a fuel transfer port allowing a cleaner transfer from the idle carburetor and the main carburetor.

This is much to do about nothing! IMHO you haven't cleared up anything.







Re: Tuning Your AMAL Carburetor [Re: Morgan aka Admin] #626614 11/21/15 5:34 am
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Don't know how much time you've got, but third post down on this page http://www.accessnorton.com/needing-air-t22136-60.html#p294786 starts a saga that might help you see what Needing has been up to.



Amateur Loctite enthusiast.
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