Hitchcocks Forum

You can polish up an Amal carb, but it's a fiddly job because of the nooks and crannies, and then it tarnishes again. Has anyone any tips for maintaining the shine on this or any other alloy parts?

As you say, difficult to polish. I spray carbs with brake cleaner and get in where I can with a toothbrush. It doesn't polish them but cleans out all the muck.

If you take it off, a Dremel buffing wheel may get into the crooks and nannies, cotton buds and electric toothbrush. A wax, which hardens, such as "Rim Wax", may preserve the shininess better than the usual coating of oil in the Autosol. Aluminium does tend to tarnish to a grey oxide unless you can seal the surface.

Amal carbs are usually some form of Zamak (zinc alloy) not Aluminium.
In my experience it doesn't take a shine as well as the more aluminium rich alloys.

Just wondering why?

Zamak is a zinc-aluminium alloy, a posh form of pot metal or white metal. Neither zinc nor aluminium cast very well in pure form, they're usually alloyed, aluminium typically with magnesium and silicon, which makes it easier to cast, weld and so on. Zamak being predominantly zinc won't polish up to mirror finish like aluminium alloys will. Would aluminium oxide abrade off and impair a carburettor, it's pretty impervious once it's passivated (formed its surface layer of oxide), or is Zamak just a cheaper alloy, or possibly easier to cast into intricate shape. We often speak of aluminium when in reality we're referring to an alloy such as 6061 or 6066 which are used for bicycle frame tubes.

Indeed, carbs are made of zinc alloys as it is easier to die cast. The melting point is much lower for one thing.

Hi Jefrs, I always knew it as Mazak!
REgards Dick.

Mazak?, Zamak? Both the same thing, Mazak being the UK name for it.I always knew it as Mazak.

Not QUITE the same Dennis. The British product was made under licence from a US company but we couldn't source the correct grade of zinc apparently, so we had to change the name. It does the same job though.