I have a 1948 rigid A7 and for years I've had either a 49T rear sprocket (sidecar gearing) or a 42T (from a later swining arm model) to choose from. The former was under geared and the latter was over geared. This winter I managed to get the 46T one I thought I needed (drum from New Zealand and bearing hub from Ireland). The engine is standard (not high compression) and uses standard type 6 carb and standard air filter so I thought the sprocket was going to be the finishing touch. But I also spent a bit of time tuning the carb with a proper exhaust O2 monitoring system. I also had a manual advance unit fitted (in addition to the standard auto advance). Firstly, it makes getting the timing right a lot easier but also, it allows you to find the 'sweet spot'. The result is a bike that now happily pulls the 42T sprocket in top gear with a drop down to 3rd only necessary for steep hills. I've seen talk previously about regearing to 42T but this is just to let folk know that it seems to be fine as long as the engine is running well. Cheers all.
