I have been building a replica Norton 500T for the last seven years and finally I am getting enough time to finish it. I plan to use a 26mm Mk 1 Amal concentric carburettor and would like to understand where to start with the jets, needle and slide. A good starting point would be what do other riders use on Ariel HT5 or similar 500 cc singles, I plan to use a simple foam air filter mounted on the inlet without an air box.

Also how do real Amal and similar replica parts compare?

Any feedback appreciated

The Burlen Webb site shows that the original carb would have had a main jet size 160 and needle jet 106.

The MK1 concentric equivalent is 626/300 which has a main 160 and needle jet 106 , so should be a good starting point for fine tuning.

I have used Burlen for parts to rebuild a MK1 concentric with good results.

Ok,I managed to get through to the Norton comp shop today.The latest factory bikes are running a 626/301 mk1 Concentric which gives a lh tickler.106 needle jet,bushed pilot and No 3 slide.For the main jet a 220 is a good starting point,but might need to go up or down depending on the amount of higher rpm road use and general engine condition.

Make sure the mag is capable before fiddling too much with low speed settings,a weak spark can come across as poor mixture settings....