Norton Atlas Breather Information
Norton Atlas Breather Modifications
The stock timed breather, which goes through the hollow camshaft, the hollow Atlas and some Commando camshafts no longer functions correctly with an offset crankshaft engine. A new breather line needs to be installed on a spigot next to the ignition unit. A breather hose is installed before the ignition unit as the hose clip holding the line in place is not accessible after the unit is installed. The new line is a rubber oil line connected to the stock breather line. Do not use a clear plastic line.
The breather line, with its branch to the oil tank, should then be connected to something like a Yamaha XS650 reed valve as this helps create a partial vacuum in the engine which improves engine performance. A modified stainless steel bolt with a hole drilled through it is supplied with all Norton Atlas crankshafts. Instructions on how to install the breather spigot, and a schematic of the breathing system, are supplied with the Atlas crankshaft too.
Breather hole location ¾” below 3/16” hole and 3/8” to left
Breather line must be installed before ignition unit is installed
Breather spigot with thin-shouldered nut
Norton Commando Breather Modifications
A new breather line spigot can be added to any location behind the timing cover. It can be connected the same way an Atlas breather line is connected or another location on the timing cavity. Some Commandos have a cover plate where an Atlas-type ignition unit might have been installed. The spigot can be installed in this cover plate. Do not use a clear plastic line for the breather line. Check on-line for other breather systems for Commando engines such as the one sold by Old Britts that replaces the cover plate or other types that include a reed valve. The original line from the end of the camshaft should be disconnected and spigot should be plugged.