Quick Tips

Quick Tips

On this page you will find a selection of technical hints and tips that we think you may find useful but don't justify a page of their own. If you can think of anything that would make a good addition, why not contact us.


  1. On a Norton gearbox replace drive side lay-shaft bearing, no. 6203 (40mmx 17mmx12mm), with a NJ203 roller
  2. Norton primary chains get tighter as everything warms up – aim for at least 1’’ up and down movement when cold. 
  3. Valve Timing on OHV Nortons. Don’t trust the dots! Inlet Opens 25°-30° BTDC. Exhaust Closes 25°-30° ATDC. Set valve timing with running clearance (pushrods free to rotate with no up and down play)
  4. Oil Bath chain cases can be made oil tight. Check they are in good condition without too many dents in the sealing surface and use some single sided adhesive draft excluding tape instead of the original rubber. As it's adhesive on one side, stick that to the inner and push the outer case on with some grease to help it slide. You'll have to work out what size you require we've bought it from Affixit in the past.
  5. Norton singles do not need a head gasket. The ones available are weak and often blow. Use valve grinding paste to lap the barrel and head together as per the OHC Nortons. If the barrel and head are that far out they can be machined to suit. You’ll never have a leaky head joint again!
  6. If fitting a new piston, especially to a single, check the weight. Work out your new balance factor. If it’s wildly different you may suffer excessive vibration. 
  7. When checking for a spark, remember that it’s easy to get a spark at atmospheric pressure but not so easy under compression in the cylinder head. The system needs to work a lot harder for this. A bigger gap will also make it more difficult to jump so a very large gap at atmospheric pressure will compare to a 20 thou gap under compression. The best way to achieve this is to use a spark plug where the earth tag has been removed to make the spark jump from the centre all the way out to edge. 
  8. When carrying spares on long journeys, or anytime for that matter, don’t be restricted by the size of your toolkit. A length of spare petrol pipe can be stored up the end of the handlebars, and most British bikes have room in the back of the headlight shell for a spare set of cables. These can then be accessed with just one screw. Failing that cable tie them up under the saddle. 
  9. Do not powder coat barrels and heads. The coating does not allow for proper heat dissipation. Stove enamelling gives a great finish that lasts forever and allows the heat to escape. These people have done a nice job of barrels and heads for us in the past.