Amal 276 slider

[ajberrow]

How easily should the slider move in an Amal 276 carb?

I have stripped the carb, gently cleaned the slider and found that it has lost a lot of its plating, is blackened in some areas and does not slide freely in the bore.

Should it move freely?

Must its plating be completely intact?

Can I buy a replacement slider?

If I buy a replacement slider, which other parts should I replace with it?

Should I just turn the carb into an ornament and replace the whole thing?

I have no idea of the 'bike's mileage. It shows 5700-odd miles on the odometer, but many other parts of the 'bike suggest a much higher mileage, so I suspect it's either done > 100,000 miles (odometer can only display 99,999 miles) or the speedo has been replaced or it's been clocked (and why would anyone bother doing that?).

Thanks,

Anthony

[twolitre]

It is usual to find a bit of scuffing on the slide. Remember that it works in totally un-lubricated state (atomised petrol sees to that)!

However, the slide will not swell or grow and neither will the bore, so if both are clean the slide should move up and down freely. If it does not it suggests distortion somewhere. Measure the slide carefully at different points with something accurate (micrometer or vernier caliper) to make sure it is round all over and not tapered. Especially the bottom edge where it can get burred over from rough handling or dropping. Check the bore also.

If you do an internet search for "Amal" you will find new parts are still available on mail order. You may even get some advice.

Jim.



 

[ajberrow]

Thank-you, twolitre.

Have ordered a vernier caliper so that I can measure it accurately.

Someone suggested a gentle rub-down with very fine wet-or-dry while cleaning more thoroughly.  Is this in order?

Anthony

[Revband]

Best not to use wet/dry paper on the slide they wear fast enough without help, try cleaning with metal polish.

Over the years some ham handed owner has probably over tightened the two mounting nuts distorting the Carb body, DON'T try and tap the flanges back if this is the case as they will snap off, Check for distortion with a straight edge across the mounting surface, if it is curved fit the Carb to its mounting without any gaskets ETC, metal to metal and tighten the nuts to gently pull it straight.

If you still have a problem there are specialist repairers who will fit a sleeve to the slide and rebore the body to fit.

[ajberrow]

The slide was not distorted, just very dirty. and I hadn't cleaned it properly.

With lots of gentle polishing, it now slides easily, it's just a little tight getting it into the top of the bore, but finger pressure is enough to overcome that problem.

Thanks, all.

[twolitre]

Revband is quite right in saying overtightening the mounting flange will distort it, but I doubt that that will distort the carb. body. I am also unsure that his method of cure can be relied upon. The correct way to correct flange distortion is either machine it flat, or alternatively by hand, by placing a piece of emery paper on a plane (very flat) surface - mirror glass will do - and rubbing the carb. flange on the flat surface, taking care not to rock it, until the signs of abrasion cover the whole surface. Then replace the carb. Tightening the nuts only sufficient to hold it securely in place. Put pressure on the spanner no more than about 2 inches (50mm for Moddies) to tighten two hole flanges. Not many people seem to realise that spanners are the length they are to UNDO tight nuts etc. and because of that MANY fasteners are often overtightened.

[Revband]

Hi twolitre

I have on more than one occasion found that a carb body has been distorted by over tightening the flange nuts where a soft heat shield has been fitted, yes you can partially remove this distortion by the method I described (usually enough to free the slide), but to flatten the mating surface as you say the only way to make it completely flat again is to dress the face.

You can tell that the body is distorted if you measure the carb bore the worst case I have had was a 1" carb and the bore measured 15/16" horizontally and 1 1/8" vertically that is bad distortion.