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.