Sleeving Vintage Amal carburator

Was wondering if anyone has ever resleeved the slide bore of a carburetor. The Amal concentric carburetors were used on vintage British motorcycles and, in fact, they are still available today. The problem is that they are made from a relatively pot metal (not aluminum). The slides are made from the same soft material. The result is a galling action leading to wear which leads to improper fuel mixtures. I would like to ever so slightly over-size and true-up the carburetor slide bore. The slide would be turned down and a brass sleeve affixed to the slide. My thoughts were that a reamer would do a more exacting job than trying to bore on a lathe. An aluminum cylinder with simple steel cutters set in the cylinder should do the job with perhaps a center shaft protruding into the needle seat hole to ensure alignment. This entire operation could be done by hand and a reamer would provide a cleaner finish. As for turning down the slide, I haven't come up with a more simplified technique Both the bore and slide are round of course. If it were only one bike I might take the plunge and buy a set of the new Premier Amal carbs. They, like my effort have a dissimilar slide but with several vintage bikes the cost begin to become prohibitive. I thought it would be worth the try as i have a couple of worn spare carbs to experiment with. There used to be a few old chaps around that did resleeving but they have taken their secrets with them.
Any ideas and suggestions would be much very appreciated. Thank you

I was sitting here trying to remember the wall thickness of my old Amal 28s on my 73 850 commando I used to have. The Amals had become so badly worn to the point that performance had dropped to near zero I mistakenly thought I wanted to adapt a pair of Mikuni 32's to it then had to down jet them. power was back in over abundance after an IGN upgrade combustion chamber clearance shave only .008" wound up replacing the clutch pack with a Barnett added a disk as well then came the primary chain upgrade which led to a 5 sp transmission then a 30 mm wider tire in the end a botched up looking and acting bike that would eat a KZ 1100 for breakfast lunch and dinner in the 1/8 or 1/4 Should have just rebuilt the Amals or bought new ones. (Available back in 1980.) If I had I might have kept the bike.
For sleeveing or bushing I am wondering if it would be possible to use an exothermic metalizing spray to do the build up. I can see this working on the slide but the smallness of the bore that might be impossible. I know there are coatings which can be applied to racing pistons to reduce friction they have a minimal build up factor
which may be a possibility for the bore and slide to build them up without having to sleeve the coating then could be honed or polished back to spec.
Might be worth looking into.

From British bikes many a mechanic was made. The wall thickness on the Amals is already on the thin side. We're talking only a couple of thousands to true things up for those who might be wondering.
I had thought that some kind of coating on the slide would work. I had considered plating the slide. Amal did have replacement chromed slides but these were recalled as the chrome had the bad habit of flaking off. The new Premier carbs have anodized slides. The problem of course is that the bore is now oversized due to wear.
Thanks Frank

Hello !! I havent resleeving an amal carb but i reore it on my sb lathe many years ago for my Royal Enfield bike , the fact was i take a few thousandscand made a new curtain i aluminium and still works fine , and extra consideration is to made new ways on the bronce block because if they are worn out makes the curtain twist and gives a very erratic idle .
Your idea to fit a sleeve is very intresting it could be nice to fit it loose and hold it with loctite to avoid stress on the pot metal then made a mandrel an hold on the lathe to exact boring
Hope it helps !!
Regards
Andrew from Argentina
Wasap +542914674259

A friend in the Tucson area was turning down Mikuni slides for Amals. I had a BSA 441 Victor that I used one of his slides on it and never had any more trouble. I didn`t do anything to the carb; just dropped the sllide in. I see now the shop he was turning them out for is still in operation and mentions turning the carb body too. Here`s a link to their process. Concentric Modification

I assume that you are doing a restoration. If not, set the AMAL concentric aside and use a decent carb. I used race a 750 Triumph twin back in the 1970s and used a pair of 32mm Mikuni carbs. Some riders were using Dellorto carbs from Italy. Sorry to the Brit bike lovers, but AMAL carbs were sh-tty. If you must use an AMAL, I would suggest trying to find one in better shape rather than trying to sleeve a worn-out one.

Thanks, but I sold all my BSAs several years ago and just sold my Harley Davidson last year. I somewhat reluctantly got out of the motorcycle scene after riding for 55 years. I did have a `65 A65 with a single carb. I replaced the Monobloc with a Mikuni 32 the day I was riding it work and smelled gas and looked down and it was spurting a stream on my leg. I`ll be the first to admit the Amals were shitty carbs. At least the concentric was an improvement over the monobloc. It was probably designed by Joseph Lucas, too, lol. (Known in British bike circles as the Prince of Darkness)

Thank you for the replies guys.
I know that with a set of Mikunis properly dialed in, the bike will run better. To my thinking it defeats the purpose somewhat. I might as well buy a new model bike which I already have anyway. These old bikes don't have an electric starter, they don't have as much power, the brakes could be better and they leak oil but it is a hobby resurrecting these old girls.
Andrew from Argentina, I am not sure exactly what you did. I realize that there is a language issue. Perhaps you could try and explain once more what you did. You made mention of an aluminum curtain. Was this aluminum piece something that was sleeved to the perimeter of the slide or did you insert a sleeve in the bore? Perhaps you could explain in a bit more detail what you did.
Baja, your chap at the linked site uses a chrome plated slide. As mentioned in my reply above, Amal started out with an improved slide that was chromed. The problem was that with time the chrome started flaking. Chrome flakes sucked into the motor is not a good thing. The other issue is that aside from the cost of sending out six carbs, I would like to keep the carbs as stock as possible whereas this chap modes the slide so that the choke can no longer be used.

Sorry my poor english , the proper name was slide instead of curtain , in my case im just rebore a few thousands in the lathe and made a slide of camplo ( kind of aluminium ) and works very well .
I wonder wich carb you have and in wich bike you fit it .
Excuse me thirdbike whats your name ?

Not sure if they still do it, but brake repair companies used to sleeve brake and clutch cylinders to reclaim them and actually make them better than they originally were. It might be worth talking to one locally to see if they still do it now. My experience with several of those Amal carbs was that the threads holding the top cap on often unscrewed or just popped off. e.g. 1960 Norton only 3 years old, straight off ferry at Calais, never driven on the right of a road before, opened throttle, cap popped off and bike accelerated to near full speed up the main street, through intersections, red lights etc etc and no idea where I was going. Key was in chest pocket of and anorak I was wearing, so only option was to turn fuel off while dodging cars with one hand on handlebars. Bike eventually used up the fuel in the bowl and stopped outside a bakers shop. It was surprising how much distance it travelled on a bowl and hose full of fuel. Sat down in the gutter for about an hour after that with fresh baking and coffee to calm my nerves.

Andres, the carbs are Amal Mk1 930 concentrics. They are for a couple of 650 and 750 triumphs. So if I understand you correctly, you simply made up a new slide from aluminum. That would resolve the dissimilar metal issue for certain.
Moby Duck, I haven't seen or heard of a brake repair business in decades. There are still lots of brake shops around mind you but today, if a brake cylinder needs attention, it is simply replaced. Labor costs and liability issues killed the rebuilds years ago. I like your Norton tale.
Still hoping someone will address the issue of reaming versus boring. With my lathe I simply wouldn't be able to get the needed finish without sanding etc which throws out the hope of exact tolerances.

Proper resleeving is possible with care IF the original mazak like 'monkey-metal' hasn't started to crumble. Though these days I'd be looking to rebuild with one of the Belzona (or JBWeld) products first then honing out to original size, even if the parent metal is doubtful.

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Originally Posted by NeiljohnUK

Proper resleeving is possible with care IF the original mazak like 'monkey-metal' hasn't started to crumble. Though these days I'd be looking to rebuild with one of the Belzona (or JBWeld) products first then honing out to original size, even if the parent metal is doubtful.

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While Belzona or JBWeld or similar products have a great range of uses and might even be a viable solution in this instance.
The bore would still have to be bored out then the product applied then bored and honed.
My concern would be life expectancy and wear factor or the possibility of fuel causing deterioration the Slide would still need to be remade.

thirdbike has also asked about the possibility of using a reamer in the bore.
If one had a fixed size reamer say .002" oversize to the bore this would probably be 1 of the better ideas but after the bore was reamed to round and clean an internal lapping or burnishing tool would be required to polish bore and a new oversized slide could be made
If the epoxy like products were used the bore would still require lapping

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Originally Posted by Frank S

While Belzona or JBWeld or similar products have a great range of uses and might even be a viable solution in this instance.
The bore would still have to be bored out then the product applied then bored and honed.
My concern would be life expectancy and wear factor or the possibility of fuel causing deterioration the Slide would still need to be remade.

thirdbike has also asked about the possibility of using a reamer in the bore.
If one had a fixed size reamer say .002" oversize to the bore this would probably be 1 of the better ideas but after the bore was reamed to round and clean an internal lapping or burnishing tool would be required to polish bore and a new oversized slide could be made
If the epoxy like products were used the bore would still require lapping

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Indeed the epoxy would require boring to size, with finishing to suit. I've been using Belzona for years and never had an issue with fuel, the Weber DCOE's I repaired with it in 1978 are still leak free, and industrial use has proven just how good a wear material it can be, a brass sleeved slide in a body lined with it would last for years. JBWeld is pretty good too, and a lot more affordable, my recent motorcycle repairs to a 10 year old BMW 'F's oil/water heat exchanger were done with it to keep costs down, fuel resistance should be ok but I've not used it in that way so I can't confirm what the manufacturer claims.

What the "original" carb rebuilders did was to clean up the carb bore to oversize and put a brass sleeve on the slide. In other words the bore is left oversized.
An epoxy product might be a option for application to the slide. I am wondering how well an epoxy product will adhere to the the pot metal especially as the slide needs to get shaved down to size. It might take a trial and error session to see how well that works out and then let it soak in the new ethanol blended gasoline.

There's a hell of a lot of Spifire pilots and old Hydro racers who would accurately argue about "the prince of darkness". Those great MERLINS ran like a mofo. In my younger days I was known as "Limey John" because most idiots with brit bikes didn't know squat about how to wire Lucas charging and ignition systems. I have NEVER had any problems with bri charging or ignition systems. The magnetic rotors used on brit bikes had residual magnetism a very hi perf feature found only on the best stuff. I also used American double lip seals when rebuilding brit engines and mine NEVER leaked. For my 2 cents there is nothing wrong with monoblocks at all and are much more tunable than the concentrics. Cliff and Sharon Majors, who owned Cycle Hub in Portland Ore got me straightened out on Amal's.

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Originally Posted by DIRTYJOHN

For my 2 cents there is nothing wrong with monoblocks at all and are much more tunable than the concentrics. Cliff and Sharon Majors, who owned Cycle Hub in Portland Ore got me straightened out on Amal's.

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Yes they are, though I'll stick with my Amal TT thanks.

I do appreciate the sentiments but would like to keep this thread focused on carb sleeving. Any tips and ideas are welcome.

Quote:

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Originally Posted by thirdbike

I do appreciate the sentiments but would like to keep this thread focused on carb sleeving. Any tips and ideas are welcome.

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Hi thirdbike,
A few thoughts on Amals, these are the carbs I have most experience with and have always found them to easy to tune and are perfectly reliable for a road bike. I have not found a worn slide or bore to be the main cause of lack of performance but more to do with worn jets and needles, the needle is free to find its own centre in the jet which leads to fairly rapid wear ( I used to replace mine at about 30K).
Obviously galling is not good but can be smoothed out, the slide needs to be a loose fit as it is only closed by a fairly light spring and any foreign matter can cause a sticking open throttle (nuf said). The later types of carbs with a cable opening /closing feature is much safer but sadly not on Amals.
The main concern seems to persieved air leaks past the slide but this only affects tickover settings which are easy to compensate.

I agree with Olderdan as that was my experience back in the day too. Did a lot of carb work back then on SU's, Amals etc. with similar arrangements. The minimal difference from alignment wear in the cylinder will only vary the mix ratio slightly, unless severely garred from 1-800 bad airfilter. I'd try a new set of needle and seats before jumping off that cliff. Another thing I used to find was the cable pull and spring would kant the piston if not all in order also. Never did like the idea of metered air leaks or triple slop to hit a tiny hole dead center.

One thought on your sleeving idea would be to use a solid round bar either epoxied or loctite in and then bore, ream and hone to proper Id. Can't remember if there were side ports in the cylinder though?? Question is: what is the ID supposed to be exactly? Used to have a great machinist guy that would do that with bronze round bar on SU butterflies and line bore and ream the set for me.

Just thoughts. You got a great thread going here!
PJ

Thank you for your input Olderdan and PJs. Yes I aggree the needles and jets wear but then again are simple and economical to replace, The wear in the slide bore occurs at the most common throttle setting, in other words at cruise. The result is that the wear in the slide is not uniform. If you were to look at it cross-sectionally there would be a belly in the bore towards the middle. The wear is inline with the air flow as the slide jiggles and vibrates in tandem with the engine. The result is you end up with what is commonly referred to as a flat spot in the bike' performance due to the air leaking around the slide rather than via the slide cutaway as the fuel is no longer being properly metered. At idle the bike still runs properly as it is being supplied through the pilot circuit and the slide is seated at the bottom of the bore. Similarly at wide open throttle the slide is now wide open and past the wear.
I trust this clarifies how the wear impacts the carb's performance.
thank you again

Ive had a BSA for 40 years, always fooling with that carb. The problem was when the carb heated up the body would swell up, and grab the slide. Since I have isolated the carb from engine heat, I have not had any problems. works awesome!! Ask me how?

At the moment I am not sure of the BSA OEM carburetor gasket thickness. The problem is compounded with many aftermarket gaskets being paper thin and poor quality. In the case of the Triumph twins, the heat transfer is even worse as they called for the use of an O ring. The carbs being made of a soft pot material and is easily distorted especially with heat. The cure I have found is the installation of the extra thick gaskets used on the Nortons. The material is hard rather than the more common compressable gasket material. As such, the carbs could be bolted up securely without the fear of distorting the flange. Keep in mind that as the flange distorted so did the slide bore go out of round. A lot of slide sticking issues were attributable to this warping. Many users simply sanded the flange flat again resulting in the removal of material from the mounting ears. This only served to weaken the ears leading to even further warping. If you have another solution, please do fire away.

Maybe these can help, I have always used them for road bikes.
The curved flange symptom is common on these carbs and is often caused by the use of a to thick O ring. To avoid over tightening I use a plain washer followed by a spring washer and nut just nipped up.

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Originally Posted by thirdbike

Was wondering if anyone has ever resleeved the slide bore of a carburetor. The Amal concentric carburetors were used on vintage British motorcycles and, in fact, they are still available today.

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I would bore the body in a lathe, taking the absolute minimum to clean it up. The Concentrics didn't have a through hole and it would be near impossible to manually ream it parallel. Once you have bored the carb I suggest making a new slide complete, That is easy enough those slides are quite simple.Iit would be best to get it hard chromed as many race Amals were, or other coating. There is a lot of choice for coatings these days that were not available in the past. If you plate or coat it then you have more choice of material to make the slide from, brass and aluminium are the traditional materials but you could use steel and machine it with a thinner wall. The Mk2 carbs have aluminium slides hard anodized.

PS. Are oversize slides available from the company that has carried on making the carbs, they do have a full range of spares.

Olderdan,
Yup those look like the gaskets that I use although I still prefer to mount the carbs using the original Cleave-Lock nuts with a plain flat washer (not the rubber backed washer) - Not really much different but to each their own I suppose.

Tonyfoale,
Unfortunately, oversize slides are not available. My guess is what size to oversize them. They did chrome slides for a few years to avoid the galling action but found that with time the chrome de-laminated and would be sucked into the engine. Anodized slides are sold as replacements and also used on the new replacement premium carbs (including a removable pilot jet). Amal ad re: 600 series Premiums follows though 900 series also available:

"As a further step in the improvement and development of our carburettors we are now offering special light weight versions of our 600 Series Premier carburettors with the body and float bowl cast in aluminium. The carburettors include all the parts developed by us for the Premier carburettor – hard anodised aluminium throttle valve, ethanol resistant Stay-up float, removable pilot Jet and aluminium needle valve and have been comprehensively tested on the road and have already clocked up several trials successes.Genuine AMAL jets guarantee accuracy and consistency of performance.
The aluminium carburettor offers a weight reduction of around ¾ lb over the traditional zinc alloy type."

I have that, and I use rubber washer under the Nybolt nut, so I don't tighten it too much.

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Originally Posted by thirdbike

My guess is what size to oversize them. They did chrome slides for a few years to avoid the galling action but found that with time the chrome de-laminated and would be sucked into the engine. Anodized slides are sold as replacements and also used on the new replacement premium carbs (including a removable pilot jet).

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What was the base metal used for those chromed slides? During the 1960s I used a very old Amal which had a brass slide chromed. Never had any de-lamination.

Attachment 27173 Click for full size image.
Slide is centred on top row.

I have a couple of original Mk2s, they had anodised slides from new, not replacements. I think that the removable pilot jets came in with the Mk2s, there were two locations, front and back. The front was the normal 4 stroke position with the rear for 2 strokes and 4 strokes with steep down draft. The rear was further divided into left and right positions.

Quote:

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Originally Posted by thirdbike

I do appreciate the sentiments but would like to keep this thread focused on carb sleeving. Any tips and ideas are welcome.

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Once you make a post the direction it takes is no longer under your control. It becomes public within the HMT community and may head off in many directions as other simulii appear and other posters respond. That might sometimes be annoying to the original poster but it is also what makes this forum great. You have to go with the flow.

Tonyfoale,
That is an old carb you have showing. They're rare.
The carbs I had been talking about were the Amal Concentric Mk1. They replaced the Monoblocs in the 60's through to mid 70's before the advent of the Concentric Mk2. The original Mk1 had a removal pilot jet but most came sealed. Only the new Premiers replacements now have removable pilot jets once again. All the Concentrics came with uncoated slides and were made from the same pot metal as the carb body - hence the galling action between the two similar metals. Again later could you buy replacement slides that were chromed and later still anodized slides. All are only available in the stock size

Quote:

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Originally Posted by thirdbike

Tonyfoale,
That is an old carb you have showing. They're rare.

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It was the only pic that I had to show the chromed slide.

I won't comment too much on changing carburetors. Few are more adaptable than Mikuni. In respect to Amal I'd avoid entirely reaming metallic type material that soft. Boring with a perfectly honed tiny radius HSS bit is far more dependable size control. In the venturi or lower with fuel in suspension a slightly unsmooth bore isn't a guaranteed detriment, but a true cylinder is important for a slide.

Ol Joe Lucas has a reputation here too. We've known his Prince of Darkness nom de plume awhile; now he's also the Duke of Fuel Fires?