Amal Concentrics seem to be universally despised by the mechanically inclined among our local Vincent club. I agree that the originals had a problem with slide wear, but that can be dealt with by purchasing the new anodized slide or by having the carbs sleeved.
Other than that, they are small, simple and work well. I have Mikunis on the one Rapide, Concentric mk 1s on the other. The bike with the concentrics is easier starting and generally goes better than the Bike with the Mikunis. I think the tickler on the Amals is helpful for cold starting. It seems more effective than the enrichener circuit used by Mikuni.
Over the years Ive had a few bikes with Concentrics and quite a few with Mikuni , Kiehin and one with IRZ, no big problem with any of them but I find the Amals to be about the simplest of the lot.
In the past a number of Commando owners have converted their bikes from twin Amal Concentrics to a single Mikuni. Now that trend is reversing with the realization that the bikes run great with the Amals plus make a whole lot more power on the dyno with the twin carbs vs single.
Similarly, it has been a popular mod to replace the original 40mm Bing on the 490 Maico with a Mikuni, the claim bein that starting and low speed running is improved. My Maico came with a Mikuni mounted and a Bing in the parts box. The owner of Canadian Maico Connection suggested I put the Bing back on. What a difference, all of the blood now rushes from my head during hard acceleration, whereas with the Mikuni on there a small portion remained trapped in my skull!
As far as starting ease and low speed manners, the bike has no low speed manners anyway and starting is about the same.
Glen