The front brake fitted to your bike is the post-1971 'conical-hub' type and is generally held in disdain. There is a lot of talk about these brakes regarding why they don't perform very well, ranging from the insufficient length of the cam-levers, the cable (rather than rod) coupling between the cams, to the theory that they were designed for hydraulic use.
For whatever reason, most people find them less-than-effective and either fit an earlier (1968-70) pattern brake or a disc, both of which are fairly easy come by but they need different fork sliders - the earlier brake takes cast-iron type whereas both the conical hub and disc require the four-stud alloy sliders.
However, that said, with careful assembly and setting up the conical hubs can be quite an adequate stopper. The process I followed on mine was:
1) Make sure the drum liner has been accurately trued up, especially if you've re-laced the wheel at any point (the alloy hubs easily distort).
2) Use new bonded-on brake-shoe linings, preferably a soft, easily warmed compound, and make sure there is very little play between the shoe and the liner.
3) Use a new teflon-lined heavy gauge brake cable.
Basically you want to make the brake as brand new so that any adjustment is kept to a minimum, and you want to only have to move the lever a matter of millimetres before the brake engages. In this way I've found the conical quite a reasonable brake. Not as good as the 1968 pattern (in my experience anyway), but much better than most reviews would suggest.
Alternatively a friend of mine converted his conical hub to hydraulic operation using a master cylinder from a Triumph motorcar with great effect. I couldn't tell you how he'd done it, but it proves it can be done if need be.
You have a very fine looking Trumpy there. I could pick holes of course like the purist I am, hahaha, but I won't because it's always nice to see another Meriden twin on the road.
Good Luck
