Anyone know why Norton chose the Amal 76AK/1AT instead of the 276?

Previously wrote:

I've mulled over this question but don't have the experience to come to a definite conclusion. The 276 actually appeared first on Nortons for the India Office military contracts as early as 1937. As you correctly say, all stub fitting instruments. Air filters were used pre-war in India and Palestine and I see no reason to doubt the story that the change was connected with this.

The 276 does not appear to have been used on anything other than military contracts. This means that it was probably either more expensive or gave less performance (which wouldn't have bothered the army too much).

The 276 began to appear on WD machines from other makes in 1940 but they all seem to have elected for a revised version, the 276R which doesn't have the flat on the jet block with the two holes in but instead a large pilot airway angled downwards through the mixing chamber.

Once again, I have no idea of the significance of this but Amals supplied the early type plain 276 to Norton right through until the end of wartime production and yet no other manufacturer specified it. There is nothing in the Amal record cards held by the VMCC to suggest that Nortons had any special rights to the design but it may be that they had helped develop it. That said, if it had been a better instrument then the Ministry of Supply would have been likely to insist that it was made available for the war effort.

Norton retained the 276 for the singles when civilian production restarted in 1946. However, Matchless who had changed to a 276R for the duration appear to have swapped straight back to the 76 post-war...

...and then Nortons put the 76 on the twin...

It occurs to me that the only disadvantage of the 76 is the inability to fit a filter and they were not standard fitments at this stage. The 276 and the 276R though do have a less smooth inlet tract and might therefore be less efficient ?

I'm sorry that this probably doesn't help much but I'm something of a whippersnapper by NOC standards too. I thought that I'd at least let you know that you're not the only one wondering about it.

I think that you'd be doing us all a service if you ran back to back tests. Do you have access to a dyno, Paul????

Rich.

Richard Payne previously wrote on Tuesday July 26th at 23.48hrs:

>The 276 does not appear to have been used on anything other than military contracts. This means that it was probably either more expensive or gave less performance (which wouldn't have bothered the army too much).<

>â?â?â?I think that you'd be doing us all a service if you ran back to back tests. Do you have access to a dyno, Paul????<

Thanks Richard. Those are a few more pieces for the jigsaw and are very reasonable theories. So with the 276 already in use 3 years earlier than I thought, it hadnât necessarily been so much the obvious way forward. Rather a timely fitment where conditions governed choice.

Jetting down and using a fine filter must have stifled the performance significantly, so Mr Hopwood

wouldnât have wanted his new twin to have been unable to keep up with the singles out of the box.

My 88 is still a long way from coming together, like all my bikes at the moment. Although North Devon has never been the hub of industrial Britain, there must be some tuning shops with dyno facilities and I do have a growing list of queries that might be answered by back to back tests like that on 650âs & Commandos.

Paul

John Whiting previously wrote on Wednesday 27th July 2011 at 13.59hrs:

Paul, the Amal 76 was reckoned to be less sensitive to flooding when hot starting,probably because the excess fuel dripped down onto the magneto.Norton produced a twin for US market called the Nomad, which had the old type carb fitted until 1960 or thereabouts.Definitely a cost cutter. Incidentally, Matchless also fitted a 76 to their twin.If you look at one of these later 76s you will see provision in the casting for the internal vent[ not drilled.], so I doubt there was any difference in the price.BSA and Triumph used 276 with provision for an air cleaner. Regards John.

Good stuff John, thanks.

I must dig out one of those BSA drip-channelsto try andkeep my 88's combustion internal.

Paul