Carb settings

The type of float has no bearing on the needle slot... although a completely wrong fuel level might obviously be a problem.

All you can do is religiously follow the published Amal tuning guide.

Current replacement Amal float needles have two slots as the plastic float that they now supply is retained by a spring clip rather than the 'butterfly' clip on top of the old float.

I only have the old set-up but I'd think that you need to use the lower of the two slots with the float chamber upright. If you use the higher one, this would raise the float level considerably which might well eliminate any effect from the air screw as petrol would be flooding everywhere (I'd expect you to see it though).

The groove for the early float is roughly 11/16" from the top so you need the other one.

Traditionally, side valves are fitted with the 'short' mixing chamber nuts but I and several I know are running 'long' (OHV) nuts on 16Hs to counter rich running. I wonder if this has something to do with the density of modern fuel. You can try an extra fibre washer above the float chamber arm as an experiment.

The man from Amal probably wouldn't say it but the most common cause of an air screw that doesn't seem to do anything is usually a blocked drilling which shouldn't be the case with a new carb but swarf blocks drillings as effectively as corrosion.

Richard - thanks for putting me right. I was thinking of the main needle - I blame the beer. I'm trying to get my 16H on the road (time...time..) and might well need your advice.

David, just as long as you don't need advice about premature valve guide wear because I'm not sure that I've cracked that one yet...

The new Amal float needle with two grooves is an odd thing - probably unique.

That's a worrying prospect. I was hoping to be maintenance-free once summer comes along (if we ever get another one). I suppose the only problem is more oil leaks? I'm already planning to carry a packet of those plastic backed absorbant paper sheets they use in maternity wards so I can put an incontinance pad under the bike when I park it anywhere posh.