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Thread: Sleeving Vintage Amal carburator

  1. #21
    thirdbike's Avatar
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    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

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  3. #22

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    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?

  4. #23
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    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.

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  6. #24
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    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.
    Attached Thumbnails Attached Thumbnails Sleeving Vintage Amal carburator-spacer.jpg  
    Last edited by olderdan; 12-22-2018 at 10:53 AM. Reason: after thought

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  8. #25
    [email protected] tonyfoale's Avatar
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    Quote Originally Posted by thirdbike View Post
    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.
    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.

  9. #26
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    We're all on the same page

    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 lb over the traditional zinc alloy type
    ."

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  11. #27

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

  12. #28
    [email protected] tonyfoale's Avatar
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    Quote Originally Posted by thirdbike View Post
    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).
    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.

    Sleeving Vintage Amal carburator-amal_tt_01.jpg 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.

  13. #29
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    Quote Originally Posted by thirdbike View Post
    I do appreciate the sentiments but would like to keep this thread focused on carb sleeving. Any tips and ideas are welcome.
    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.

  14. #30
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    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

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