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Thread: Sleeving Vintage Amal carburator

  1. #11
    thirdbike's Avatar
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    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.
    Last edited by thirdbike; 06-20-2018 at 12:49 PM.

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    Supporting Member NeiljohnUK's Avatar
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    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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    thirdbike (06-20-2018)

  4. #13
    Supporting Member Frank S's Avatar
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    Frank S's Tools
    Quote Originally Posted by NeiljohnUK View Post
    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.
    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
    Never try to tell me it can't be done
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    thirdbike (06-20-2018)

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    Supporting Member NeiljohnUK's Avatar
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    Quote Originally Posted by Frank S View Post
    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
    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.

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    thirdbike's Avatar
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    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.

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    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.
    Last edited by DIRTYJOHN; 06-20-2018 at 05:14 PM.

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    Supporting Member NeiljohnUK's Avatar
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    Quote Originally Posted by DIRTYJOHN View Post
    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.
    Yes they are, though I'll stick with my Amal TT thanks.

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

  11. #19
    Supporting Member olderdan's Avatar
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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.
    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.

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    PJs (06-21-2018)

  13. #20
    PJs
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    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
    ‘‘Always do right. This will gratify some people and astonish the rest.’’
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