Amal Carburetor Slide Metal?

The concentric carb I bought in 2000 had a mazac slide.  When I was happy with it, I bought a chrome plated slide, but no idea what's under it.  Anodised aluminium slides weren't advertised then.  Why not buy one ready made?  Anodising isn't a homework job, so having one done specifically must surely cost more?

Sorry.  I hate it when people answer the wrong question...but nobody else has come up with anything yet.  I thought they were Mazak (or Zamac) - as I'm sure you know they are much the same. Exact details will be 'commercial in confidence'!  Mazac was well known for decaying with age (as Dommie chromed tank flashes often do).  I think Amal used better metal quality control because they don't seem to suffer.  Hopefully someone else will offer some info.  But (unless someone knows different) I'm sure they didn't use aluminium at that time.  Weren't there some stories about some chrome plated slides having sharp surfaces and that's why anodised aluminium slides appeared?  In other words - they were Mazak or chromed Mazak or anodised aluminium.  (I remember considering anodozing something but decided it was too complicated for me!)

Received wisdom has it that the originals wore badly as both slide and body were made of the same material. Monkey-Metal so highish zinc. Certainly never with nice anodised slides like Mikunis of the same period.

I've seen earlier (276) Amals delaminate and burst with metal rot, but never Concentrics.

Two years ago, I purchased a new £180 Premier 930 Concentric, with an anodised slide, for my Norton 650. It was jetted as for a single carb Mercury 650 and this initially worked well. However, after about 1000 miles of riding, the engine cut out one day on a journey home from a visit to The Fleet Air Arm Museum. It then restarted but would only idle. I diagnosed a block jet with the carb and fortunately had taken enough tools, with me to do a roadside dismantle.

Removing the float bowl drain plug revealed large black lumps. As in photo below. I got home OK and did a postmortem.The problem could not be rubbish from the fuel tank as I had a petrol tap filter, an inline paper filter and the fine mesh carb filter in the feed system. All the carb innards looked fine so I put the problem down to chunks bedding in with each other and causing fine debris.

Another 1000 miles later and this time I got stranded on the M27. Then 6 months later it was the Chichester bypass. I now clean the carb float bowl every 1000 miles to pre-empt similar strandings. 

The cause???  Well the main jet blocking lumps are all black and crumble into powder when squeezed. So I am guessing this is residue from the black anodised slide. Is this due to frictional forces or has Ethanol got something to do with the problem?

Can't be from the slide unless they are able to pass down the slide needle and through the main jet?  Surely anything off the slide would disappear down the inlet port and go through the engine.

Are you sure it isn't the inside of the fuel hose or something like that? Is the float black?

Just wondering. 

George 

Have you lined the fuel tank?

Its the effect of that wonderfull fuel supliment called thanol that we all love.And its so good that we have the choice to have it ,   or not !!.

20,000 miles on premier slides and look just like the day they were new. 

George....I agree with you.  How does this debris get into the float bowl?  As mentioned in my scribble above....I have three filters between the tank and the Carb. The tank filter now regulary gets a free coating of rust thanks to the Ethanol in the fuel. The centre cartidge filter goes grey/light brown every year, so appear to be doing its job. The carb fine mesh filter looks as new each time I clean the carb.

The throttle slide was the only all-Black component (it is now dull grey) and despite an air filter is showing signs of very fine scoring. The body of the  Premier has now changed from a shiny silvery finish to typical grey alloy of a well used Amal carb. 

The other point worth a mention. When new......starting my 650 engine needed full choke, a minute or two of warming with half choke and then some choke to pull away. After around a mile of riding, the choke could then be eased off. This is how my Commando behaved when treated to a new Premier carb. However, nowadays......the 650 start procedure is tickle, two kicks with half choke, igintion off, then power on, kick and the engine generally fires up. Choke fully off and away we go.

Something has clearly worn inside 6,000 miles of useage. I still believe that the cause is connected with Ethanol in the fuel. All the Esso stations where I live are now 5% contaminated.

This week, I am going to refit the old Wassell 930 that was on my 650 before the Premier arrived. The bike starts easy with this carb but refuses to idle.