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Re: Tuning Your AMAL Carburetor [Re: Tiger] #220303 10/23/08 4:12 pm
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Amal Technical Offline
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My attention was drawn to this thread and I thought I might be able to add some information about the history of the Mk1 AMAL Concentric carburetter.

Some engines are more sensitive to fuel level than others when fitted with this carburetter, although in general terms the design can accomodate variations in fuel level due to the range of manufacturing tolerances. Back in 1998 whilst working with Tom Ullman at Grosvenor we investigated a production problem that came about due to the poor moulding of a batch of plastic floats. This investigation highlighted several anomalies. In addition to the badly formed tag on the floats it was discovered that the introduction of machining the gasket face of the float bowl had effectively raised the support for the float pivot pin, which altered the geometry of the float action. This machining operation had become necessary to overcome the deterioration of the cast face that was a possible source of leaks. The casting die was subsequently altered to return the part to drawing tolerance. At the same time an additional gauge was introduced to the manufacturing process to ensure the float also conformed to drawing.

The final outcome of this investigation resulted in, not a design change, but a return to the original AMAL drawing parameters that had deteriorated over time due to tool wear.

When AMAL was sold to Burlen Fuel Systems Tom and I oversaw the transfer to ensure the continuity of manufacturing techniques.

During the last couple of years the original tooling reached the point where it was no longer possible to produce a quality product and AMAL took the major step of investing in new tooling to produce the 900 Series Concentric Carburetter. This new tooling has seen a significant improvement in the quality of the carburetters which are now becoming more widely available.

AMAL are continuing to develop the Mark 1 Concentric Carburetter and intend to introduce a number of improvements in the near future.

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Re: Tuning Your AMAL Carburetor [Re: Amal Technical] #224055 11/18/08 3:01 am
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Alex Offline
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So, I'm trying to adjust the float level on a 389 Monobloc and I can't for the life of me find a spec for the fuel level. I'm using a sight tube to indicate the fuel level. I've done this before but it's been a while and I can't remember where I found the spec. Anyone know or have a source? Thanks.


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: Alex] #224059 11/18/08 3:10 am
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Never mind, I just started digging through every manual I had and finally came upon Rupert Ratio. The fuel level should be even with the raised dot on the bowl cover.


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: waspfarmer] #225179 11/25/08 1:41 am
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Originally Posted by waspfarmer
Richard,
Around '69? Amal changed the position of the pilot jet. It used to be visible in the bottom of the carb body and threaded in. Later, the pilot jet was moved to exist accross from the air adjustment screw. If you remove the air screw, you may see it with suitable lighting. There's a carb mod to gain access to the repositioned pilot jet that invoves drilling and tapping for a shortenned air screw (to blank off) opposite the present air screw. The orriginal threaded position remains on the bottom of later carb bodies leading one to believe the pilot jet is missing! It's not.


So, that means that if the pilot bush is there the pilot jets can be left off and their holes left open?
I just opened up the 930s on my 71 Lightning and found pilot jets installed. Looking in the hole left by removing the air screw I can see the pilot bush.
Guess I'll have to get a 78 bit to check them out for correct size.


Stepping on others doesn't make you stand tall.

71 A65L "Zelda"
92 BMW K100rs "Gustav"
72 T120V cafe project "Mr. Jim"
72 T150V "Wotan"
Re: Tuning Your AMAL Carburetor [Re: waspfarmer] #225675 11/28/08 12:12 am
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DavidP Offline
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Originally Posted by waspfarmer
Richard,

Work the slide up and down and observe where contact is made. Carefuly and as focally as possible sand that puppy good! Repeat.


You got that right. I just bought new slides and had to spend over three hours sanding the bores to get them to fit.
There's still a bit of sticking, but I'm sure that a bit of fuel and vibration will get them free in operation.
So much for quality control in casting.


Stepping on others doesn't make you stand tall.

71 A65L "Zelda"
92 BMW K100rs "Gustav"
72 T120V cafe project "Mr. Jim"
72 T150V "Wotan"
Re: Tuning Your AMAL Carburetor [Re: DavidP] #226423 12/02/08 11:07 pm
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John Healy Offline
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David: Sanding is not the way to do this, as the body should be straightened. Using vibration, instead of a proper mechanical repair, is a good way to experience an early death, or worse.

The body of your carb is warped from being over tightened. For a new slide to fit the warped body the body must be fixed. That means bent back to the shape it left the factory. This is the first thing that is done when you send your body out to be sleeved. It is done with a simple tool that can be made with a lathe and drill press.

We covered this in Vintage Bike and quite a few people copied the tool illustrated in the article.


Re: Tuning Your AMAL Carburetor [Re: John Healy] #226456 12/03/08 5:49 am
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DavidP Offline
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John: If I'm going to pay for that I might as well buy new MkII carbs or Mikunis.
I never had this trouble with my Trident. Why didn't those design engineers go with rubber mounting in the first place. Idiots!


Stepping on others doesn't make you stand tall.

71 A65L "Zelda"
92 BMW K100rs "Gustav"
72 T120V cafe project "Mr. Jim"
72 T150V "Wotan"
Re: Tuning Your AMAL Carburetor [Re: DavidP] #226910 12/06/08 4:39 pm
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John Healy Offline
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The fact that the "those design engineers"or the person over tightening the securing hardware were idiots doesn't make the consequences any more appealing.

The popularity of soft paper manifold heat spacers/gaskets, instead of the harder phenolic ones, increases the chances the "idiot" owner/mechanic bends the body.

The fact that the Trident's carburetors securing hardware is out of reach keeps the average owner or "mechanic" from "improving" things. We all know "more is better!" It is almost impossible to introduce the soft paper heat spacers, and resultant increased chances the body will be warped, into the T150 manifold platform due to space considerations.

You do not have to re-sleeve the carb bodies to straighten them. In fact the body must be straightened before it is sleeved. Often it is the only thing needed to correct an unruly Concentric. Removing metal from the slide bore, by whatever method you choose, only hastens the the purchase of a new carburetor, re-sleeving or increases your frustration with the instrument.

I think you will find that the people who have learned to straighten, rather than further destroy, the body have been amazed how simple it is to do. If you choose to have the body sleeved in the future you have started the process yourself. With the exception of carb bodies that are badly worn on the lower back side (where you have introduced an manifold air leak which disrupts the idle circuit), straightening the body will return full function to the carburetor.

A lot has been learned about these carburetors, and how to work "with" them, in the 30 odd years they have been around. Of course you are free choose how to approach things...

The tool I use is made from a bolt and a couple pieces of scrap aluminum. Yes, I have the tools to work with, but it isn't all that hard to do!
John


Re: Tuning Your AMAL Carburetor [Re: John Healy] #226916 12/06/08 5:53 pm
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Ger B Offline
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John, with all respect, but...
The AMAL Concentric on my BSA A-65T warped even with an aluminium spacer between the oval flange and the manifold.
And although I'm a few pounds to heavy (at least my wife thinks so), I do know how to tighten and not to overtighten a couple of nuts.

When mr AMAL Technical promises in october 2008 that he is going to solve problems with the Concentric carburettors, he is, in my view, 25 years to late.


Ger B

Re: Tuning Your AMAL Carburetor [Re: Ger B] #226934 12/06/08 8:10 pm
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John Healy Offline
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Originally Posted by Ger
John, with all respect, but...
The AMAL Concentric on my BSA A-65T warped even with an aluminium spacer between the oval flange and the manifold.
And although I'm a few pounds to heavy (at least my wife thinks so), I do know how to tighten and not to overtighten a couple of nuts.

When mr Amal Technical promises in october 2008 that he is going to solve problems with the concentric carburettors, he is, in my view, 25 years to late.


Then, Ger, with ALL due respect you did over tighten the carburetor nuts... The carburetor bodies don't bend all by themselves.

That is, unless you have had the carburetors sleeved, in which case too little slide clearance was provided. For all this to work he slide MUST have at least .0035" clearance in the body! The standard jetting is based upon this and any less both increases the chances the slide will stick, and will make the carburetor run rich, especially al idle and low throttle openings.

Some choose to argue about all this and others have learned to work with it.
John



Re: Tuning Your AMAL Carburetor [Re: Ger B] #226935 12/06/08 8:11 pm
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John:
I wasn't talking about the idiot owner, I was talking about the idiot design engineer who didn't specify rubber mounting in the original spec.
In my case, I've found that anything over 3 lb/ft causes the slides to hang up.
She runs well now, and WD40 reveals no intake leaks. But, I'll be saving my coins for some MKIIs.

Cheers


Stepping on others doesn't make you stand tall.

71 A65L "Zelda"
92 BMW K100rs "Gustav"
72 T120V cafe project "Mr. Jim"
72 T150V "Wotan"
Re: Tuning Your AMAL Carburetor [Re: DavidP] #226941 12/06/08 9:34 pm
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John Healy Offline
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[quote] I was talking about the idiot design engineer{/quote]

Those brilliant designer engineers, Jeff Binks and Barry Johnston, were responsible for the Concentric based upon an ultimatum by the major factories of the day to provide a carburetor that was cheaper to produce than the Monobloc. It was not their first choice and at the time they were working on the MKII. The MKII was more expensive to make and required additional space as it was larger and hardware to mount. The factories, who were extremely price conscious, put extreme pressures on suppliers to provide parts as cheaply as they could. Given the parameters provided by the manufacturers of producing a carburetor for a couple of pounds I think they did a very good job.

While the factory was pushing for an ever cheaper design, Jeff and Barry were also working on what was to become the MKII which was first produced as the Mikuni VM (AMAL had a close licensing agreements with Mikuni on technology dating back to 1932.)

So don't blame the engineers, it was the accountants, and the value of the British Pound, that gave you the Concentric. The US being Triumph's largest market and the Pound at $5.00 every thing the accountants could do to keep the price competitive was on the table.

So instead of complaining about your warped Concentric, why don't you fix it? Barry and Jeff didn't over tighten the nuts and bend the body.
John


Re: Tuning Your AMAL Carburetor [Re: John Healy] #226942 12/06/08 9:44 pm
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Ger B Offline
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John you write nonsense. I handeled spanners and wrenches and tightened nuts professionally for over 35 years. I did not overtighten these nuts. The Amals warp even when you tighten the nuts between your fingertops.


Ger B

Re: Tuning Your AMAL Carburetor [Re: Ger B] #226944 12/06/08 10:34 pm
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John Healy Offline
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Ger,
I love it! smile


Re: Tuning Your AMAL Carburetor [Re: John Healy] #226989 12/07/08 8:55 am
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"So don't blame the engineers, it was the accountants, and the value of the British Pound, that gave you the Concentric."

John:
I did not blame them for the design of the Concentric. I happen to like Concentrics for the most part.
I do blame them for deciding to mount the thing directly to the head instead of rubber mounting.
That flange is idiocy when a simple piece of rubber hose works better.


Stepping on others doesn't make you stand tall.

71 A65L "Zelda"
92 BMW K100rs "Gustav"
72 T120V cafe project "Mr. Jim"
72 T150V "Wotan"
Re: Tuning Your AMAL Carburetor [Re: DavidP] #227001 12/07/08 12:42 pm
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Ger B Offline
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Maybe it was not them, the Concentric designers , who desided to flange mount the carburettor but the engine builders.
Still, as a consumer in the after market, I refuse to accept the fact that a newly bought carburettor, from the box, alleady needs a modification in order to work proporly. What I mean is either a resleave modification in order to overcome the problem of an aluminium slide in an aluminium housing, or the purchase of a separate chromed slide. First year in a technical school allready teaches us that two equal or near equal materials in a friction / moving contact chew eachother away.
That's a problem which could have been solved long ago. If not for the bike builders than for the bike users like us, who maintain old bikes, and like to ride them safely. I would not have complained to pay 10 or 12 Euros (12 or 15 Dollars) more for an AMAL which would still be OK today. Now I have to throw it away, after three years, and install another one.
A JRC flat slide in my case.
No I'm not angry. Just disappointed. frown


Ger B

Re: Tuning Your AMAL Carburetor [Re: John Healy] #228181 12/15/08 5:52 am
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Originally Posted by John Healy
David: Sanding is not the way to do this, as the body should be straightened. It is done with a simple tool that can be made with a lathe and drill press.

We covered this in Vintage Bike and quite a few people copied the tool illustrated in the article.


John: If you could publish pictures of this tool here it would be most excellent.


Stepping on others doesn't make you stand tall.

71 A65L "Zelda"
92 BMW K100rs "Gustav"
72 T120V cafe project "Mr. Jim"
72 T150V "Wotan"
Re: Tuning Your AMAL Carburetor [Re: DavidP] #229457 12/23/08 10:09 pm
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stu88 Offline
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I haven't read all 7 pages of this thread, but on my BSA I had the dreaded sticking problem on one carb if it was much more than finger tight. I found the flange was slightly bowed, and got it flat with emery cloth mounted on plate glass. There was very little improvement, so I turned my attention to the Tufnol insulating block, and this were way out of true. After I refaced it, I could tighten the carb at a point I felt was correct, and no more sticking. I also left out the rubber O ring, which seems to me to assist bowing, and the bike now idles perfectly.


I am 79, not riding anymore because my knees and balance are shot.lasr bike was a 74 commando.
Re: Tuning Your AMAL Carburetor [Re: stu88] #261442 06/27/09 11:45 am
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jagxke46 Offline
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Used vice grips with towel over slide body, found where slide binding with piece of paper slid in, then GENTLY squeezed vise grips until body not so out of round. Worked fine. Monobloc A10 1960 GF Pete


Pete J.
Re: Tuning Your AMAL Carburetor [Re: chardinej] #276307 09/25/09 3:08 pm
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I am fitting a 389 to my 500 Bullet. There is no tang on the float, so i must assume the float level is raised by shimming the float needle beezle. Is this correct ? Do the shims have to be manufactured, I have never encountered anything like this in the 3 billion blogs.

Re: Tuning Your AMAL Carburetor [Re: dogbone] #278444 10/11/09 6:33 pm
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marinatlas Online Content
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Hi there, had just found a new "two stroke" AMAL MKI 30mm, and want to know if I can use it on my Norton G15 (with the appropriate manifold), as soon as I change the pilot jet(it's a 107) , jet needle ,and jet holder .....??

Re: Tuning Your AMAL Carburetor [Re: marinatlas] #294362 01/17/10 12:50 pm
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Hi All,

Been following the AMAL stuff a bit, what with stories of aftermarket needles jets etc., all the parts changes and subsequent traps for those assembling carbs from boxes of bits (like I have done).

Just came across this on the AMAL (Burlen) site.

Has lots of useful info.

http://www.amalcarb.co.uk/TechnicalDetail.aspx?id=11

Cheers


BSA 1969 A65F
BSA 1966 A65H
Triumph 1968 T120
Kawasaki A1R
& too many projects!
Re: Tuning Your AMAL Carburetor [Re: BrizzoBrit] #301249 03/04/10 3:16 am
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John Healy Offline
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Straightening bent flange

By placing a bar of aluminum turned to the diameter of a slide and machined so as to mimic the bottom of a slide you can straighten AMAL MKI bodies after someone over tightened the bolts securing the flange. No metal is removed from the body, so slide clearance is not changed.

Last edited by John Healy; 03/04/10 3:18 am.

Re: Tuning Your AMAL Carburetor [Re: Tom Mortensen] #323698 07/19/10 3:57 am
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rappy Offline
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because the float is on a fixed pivot, raising the seat will allow the fuel level to shut off sooner thus lowering the fuel level in the bowl.

Re: Tuning Your AMAL Carburetor [Re: Morgan aka Admin] #341630 11/05/10 11:29 pm
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Well.. blokes I have an intriguing equation which I thought the Hexperts might like to consider.

My Trident project ~ Standard engine except for the fact that I moderately gas flowed the head. Then a Viking 'Big Bore ' exhaust, T120 mufflers and standard original MkI Amals, and Tri-Spark ignition.

Now since first riding the bike ~ I have moved from the original T150 with standard jetting to a second set of T160 carbs with same standard jetting and #4 cutaways.

(Floats correctly set to < 2mm> below chamber edge ! Slide action smooth and steady as required.))

Since then the starting has improved as well ~ now takes only one or two strokes (again) ~

The bike runs and rides great but has low rev issues. the starting from cold really requires choking till warmed up.

But the #2 set has eliminated a definite flat spot from (throttle flick) , but is being a pli'nk to smooth out on idle.

Now it has improved since I raised the needle to the third slot.

(It has new rubbers and gaskets etc etc of course being a new bike. Surfaces have been planed/ sanded what ever you prefer.)

The top chambers have been sealed to eliminate air leaks.

Now add in 700 metres above sea level!

My theory at this point with extensive road testing as I have not yet been passed by the roads and Transport, (despite some road work of say 50 miles!) that the issues lay with the big bore pipes and a very full flow mufflers plus the altitude.

Now IMO I need to consider stepping the mains jets to 160s , BUT the question I am asking should i increase the splash jet size as well~

Bloke down the road with his A75 Rocket III , has changed nothing on his triple. But his bike is bog standard 69 Rocket!

BUT he did have to change to #4 cutaways to get this A65FS (1970) to run better! Glynn is of the opinion I really should just get the thing on the road and run up several hundred miles to allow the bike to settle down, of course monitoring the colour of plugs etc to ensure correct mix.

I would like to get it on the local dyno in Cairns for assessment~ )

Would like to hear your input ..

Cheers; Stuart SS

Last edited by Stuart SS; 11/05/10 11:29 pm.

ABSTINENCE;" He neither drank, smoked, nor rode a bike. Living frugally, saving his money, he died early, surrounded by greedy relatives. It was a great lesson to me. "
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