Amal Premire Carbs
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The biggest contributor to wear in an Amal carburetter since the demise of lead in fuel has been the use of a body and slide made of the same material. Sleeved Amals last for high mileages because the surface materials of the body and the slide are dissimilar.
The anodised slides have an extremely smooth surface which offers less friction resistance than chrome, brass or stainless steel as a slide material.
The anodised slides have an extremely smooth surface which offers less friction resistance than chrome, brass or stainless steel as a slide material.
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ebsbury said:
As there is a high proportion of lead in the pot metal Amal carbs are made from, how on earth can lead free fuel make any difference to how quickly they wear out!
Mikuni, Keihin, and Dell Orto dont sell carbs which wear out almost as quickly a tyre, so I wonder why exactly buyers of Amal carbs are expected to put up with this?
Amal carburetters are made from a composition of Mazak, a family of zinc alloys with a base metal of zinc and alloying elements of aluminium, magnesium and copper. Impurities can include lead which typically comprises a maximum of 0.005% of the composition.
I think it would be completely wrong or utterly ignorant to describe this as "a high proportion of lead".
I think it would be completely wrong or utterly ignorant to describe this as "a high proportion of lead".
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"utterly ignorant"
you nailed it.
CNN
you nailed it.
CNN
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ebsbury said:
As you seem to be very well informed, maybe you could tell the many users of this forum who have had problems related to worn out Amal carbs, of the specific reason they are made out of materials which on the face of it seems to be totally unsuitable?
My mistake for thinking the Amal pot metal had a large amount of lead it it............just thought that might have been the reason for the Amal being almost double the weight of a comparable size modern carb!
As for hard anodised slides, and dipping the pot metal bodies in some sort of short lived coating, I wonder if you can explain why Amal cannot manufacture carbs in the same way as people like Mikuni, Keihin and OKO, so they do not need these ridiculous alterations to increase the very low short service life of these carbs a little?
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Jeandr said:
OK, Jeandr........an extra 500 miles :lol:
Bring back the butterfly carburator! No wear!
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Amal carbs bodies and slides are die cast. Dies are expensive. Dies to cast zinc alloys cost half the price of dies to cast aluminum. Somebody in 1964 decided to pay for dies for zinc and not for aluminum.
The other, more modern carbs mentioned are all die cast aluminum. Aluminum lasts longer. Zinc cannot be anodized. So we can conclude that the new owners are either casting or machining from bar new aluminum slides and anodizing them. Like JRB said hard anodize is thin, but it is hard and slippery.
This ought to be a big improvement. If they bought new dies for casting aluminum carb bodies, they'd have to sell enough carbs to pay for $75,000 in new tooling I would guess. Those might be some expensive carbs.
The other, more modern carbs mentioned are all die cast aluminum. Aluminum lasts longer. Zinc cannot be anodized. So we can conclude that the new owners are either casting or machining from bar new aluminum slides and anodizing them. Like JRB said hard anodize is thin, but it is hard and slippery.
This ought to be a big improvement. If they bought new dies for casting aluminum carb bodies, they'd have to sell enough carbs to pay for $75,000 in new tooling I would guess. Those might be some expensive carbs.
Seriously? Really?
From Dynacast...
Zinc anodizing may be applied to all of the conventional die castings and ZA alloys, but ZA-27, as with plating, requires special consideration.
Zinc anodizing bears no resemblance to aluminum or magnesium anodizing and should not be compared with them. The process deposits a semi-fused composite build-up of zinc oxides, phosphates and chromates, which is deposited via an anodic spark discharge at high voltage. The basic process produces a moss green finish, typically 0.03 mm thick, but the dimensional increase in the casting is about 0.025 mm per side. Grey, charcoal and brown coatings, which provide additional protection at increased cost, are also available. The coating is non-conducting, which causes the current to intensify on areas with the thinnest coating. This characteristic ensures an even coating on irregular surfaces and deep recesses, including blind threaded holes. The coating exhibits good impact and abrasion resistance, and is non-conductive when in contact with dissimilar metals, preventing galvanic attack. It is not recommended for parts that will be severely cold-formed. Zinc anodizing provides excellent corrosion resistance, even when scratched through to the base material. Tests have shown little or no corrosion after periods of exposure of up to 2 years in salt, industrial and rural atmospheres, and exposure to detergents, oils, road salts, hot and cold water, most organic solvents and weak acids. It also provides an excellent base for paints and lacquers.
From Eazall...
A special zinc anodizing treatment is available for zinc castings. This coating is completely different than that for aluminum alloys. Zinc anodizing is a functional coating providing maximum corrosion resistance in atmospheric and marine environments.
Since the process uniformly coats deep recesses and threaded areas, anodized zinc alloy castings can serve as an economical alternative when replacing traditional brass, bronze and stainless steel components.
As Detective Friday said, "Just the facts, Ma'am" Again, not starting a flame war pertaining to metal treatment and coatings, rather presenting facts as I know them. Nothing more.
Not only did amal use mazac in concentric carburettors they used it in monobloc and remote bowl carbs prior to that. with the 289 remote bowl carbs at least they used a brass slide. Not only is the wear property of the material high the bigger problem is that the mazac will continue to expand and distort throughout its life. It is the continual distortion of the mazac and the high spots continually wearing off that accelerates the wear.
Mazac was also used for other motorcycle castings. Early BSA golden flash and similar, and Ariel in their square 4 used mazac as the oil pump body. A couple of years ago I restored a square 4 which had been laying idle for over 40 years. The oil pump was seized. I immersed the oil pump in penetrating oil for over 2 weeks and each day I tried to turn the pump. Eventually I got a little movement and was able to dismantle the pump. the gears were seized in the body and I eventually worked them out. The gear holes within the pump body were a smaller size than the diameter of the gears. After doing some research I found out about the continual expansion/movement of the mazac. I made up a cutter and enlarged each gear hole to the correct size and got the pump serviceable, but as I could not trust a material like mazac for the heart the bike I fitted an oil pressure gauge and rode with one eye permanently watching the oil pressure. I then found a parts supplier had a batch of cnc machined steel pump bodies made. I promptly bought one and installed it.
No wonder the british bike industry got such a bad name when they chose to save a couple of pennies per bike by using inferior materials.
ando
Mazac was also used for other motorcycle castings. Early BSA golden flash and similar, and Ariel in their square 4 used mazac as the oil pump body. A couple of years ago I restored a square 4 which had been laying idle for over 40 years. The oil pump was seized. I immersed the oil pump in penetrating oil for over 2 weeks and each day I tried to turn the pump. Eventually I got a little movement and was able to dismantle the pump. the gears were seized in the body and I eventually worked them out. The gear holes within the pump body were a smaller size than the diameter of the gears. After doing some research I found out about the continual expansion/movement of the mazac. I made up a cutter and enlarged each gear hole to the correct size and got the pump serviceable, but as I could not trust a material like mazac for the heart the bike I fitted an oil pressure gauge and rode with one eye permanently watching the oil pressure. I then found a parts supplier had a batch of cnc machined steel pump bodies made. I promptly bought one and installed it.
No wonder the british bike industry got such a bad name when they chose to save a couple of pennies per bike by using inferior materials.
ando
ntst8
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Crikey this topic seems to get some people quite excited.
If you don't like 'em don't buy 'em, but i for one am appreciative that Amal still exist and that Burlen seem to be working to improve the product, and still at a more than reasonable price.
My 5 year old Ducati is, despite a good local dealer, more difficult and more expensive to get parts for than my 67 and 38 year old Nortons. We don't know how lucky we are.
If you don't like 'em don't buy 'em, but i for one am appreciative that Amal still exist and that Burlen seem to be working to improve the product, and still at a more than reasonable price.
My 5 year old Ducati is, despite a good local dealer, more difficult and more expensive to get parts for than my 67 and 38 year old Nortons. We don't know how lucky we are.
Imagine how many carbs would have been sold if Amals were made with better materials.
How many Amals have been sold because they are made from poor materials?
For the price and quality of other brands available I personally can't see why Amals are still made.
As ntst8 says, "if you don't like them don't buy them"
graeme
(12k miles and worn out,,,,, 27k miles and Mikuni still like new)
How many Amals have been sold because they are made from poor materials?
For the price and quality of other brands available I personally can't see why Amals are still made.
As ntst8 says, "if you don't like them don't buy them"
graeme
(12k miles and worn out,,,,, 27k miles and Mikuni still like new)
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The point of this thread seems to be that Amal can get away with producing very poor quality carbs made using inferior materials, and seem to believe buyers will accept the fact that different slides and a ridiculous wipe off coating over the carb bodies, will mean their products are then comparable to those made by reputable manufacturers!
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ando said:
Very interesting post, and come to think of it Amal carbs do indeed seem to suffer from levels of distortion far greater than you would have expected to have resulted from over tight carb mounting nuts?
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ebsbury said:
As the subject of rapidly wearing Amal carbs is of obvious interest to anyone who owns a bike which has these fitted, I wonder if you would be good enough to explain why exactly Amal continues to use materials and production methods, which means their products are always going to be inferior to those produced by reputable manufacturers?
It has been well documented that Amal were under constant pressure from the motorcycle industry who refused to accept new instruments unless they were cheaper than their predecessors. The pre-war mazac Type 76 replaced the earlier bronze Type 6 which needed much more individual finishing.
This is all a matter of history and we can't change it now.
I don't think it fair to compare Burlen / Amal with current suppliers of OE carbs or developers of new instruments. They exist to supply the niche market of replacements for historical vehicles which are now at least 35 years old and I for one am glad that they do that. I find it quite remarkable that I can order jets and needles for a seventy-year old carb off the shelf.
I realise that there are those who are convinced that they can extract a quart from a pint pot and are trying to make a modern motorcycle out of the Commando and good luck to them but personally I'm quite prepared to accept the difficulties which come with machines of this age.
As far as I'm concerned, if you want a modern bike then buy one but please stop trying to bring down a small company which in my opinion is doing a bloody good job supplying parts for ancient machinery.
The fact is that by any logical criteria, the Commando is inferior to the products of modern 'reputable' manufacturers. Thats why Carbonfibre neither owns, nor wishes to own one but he does seem to enjoy picking holes in them.
This is all a matter of history and we can't change it now.
I don't think it fair to compare Burlen / Amal with current suppliers of OE carbs or developers of new instruments. They exist to supply the niche market of replacements for historical vehicles which are now at least 35 years old and I for one am glad that they do that. I find it quite remarkable that I can order jets and needles for a seventy-year old carb off the shelf.
I realise that there are those who are convinced that they can extract a quart from a pint pot and are trying to make a modern motorcycle out of the Commando and good luck to them but personally I'm quite prepared to accept the difficulties which come with machines of this age.
As far as I'm concerned, if you want a modern bike then buy one but please stop trying to bring down a small company which in my opinion is doing a bloody good job supplying parts for ancient machinery.
The fact is that by any logical criteria, the Commando is inferior to the products of modern 'reputable' manufacturers. Thats why Carbonfibre neither owns, nor wishes to own one but he does seem to enjoy picking holes in them.
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A carburettor by its very nature needs to be manufactured to very exacting tolerances, using the proper materials and production methods. Like it or not the Amal carbs being made today, are no better than those made 40 years ago, which means anyone who uses them has to face the consequences of rapid wear, and the poor performance that will result.
Fitting modern carburetion to any older bike is not something that is irreversible, and as this is something that will improve performance, reliability, and give increased gas mileage, and its perhaps one of the most sensible modifications for anyone suffering the effects of 1930's style carburetion, who is interested in riding rather than maintaining 100% original appearance?
Fitting modern carburetion to any older bike is not something that is irreversible, and as this is something that will improve performance, reliability, and give increased gas mileage, and its perhaps one of the most sensible modifications for anyone suffering the effects of 1930's style carburetion, who is interested in riding rather than maintaining 100% original appearance?
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