The Norton twin cylinder engine creates a serious amount of pressure in the crankcase as the motor spins. Over the years the factory attempted several methods to reduce this pressure – from a timed breather off the end of the cam on earlier motors, to a crude straight pipe from the timing chest on later 850s. While their intentions were good, none of these designs could effectively keep up with a pumping parallel twin motor at high revs.
Our NYC Norton Reed Valve Breather effectively releases pressure from the crankcases on the down stroke while preventing air from returning into the motor on the up stroke, creating a negative pressure situation which can eliminate leaks and boost performance. Originally designed by Comstock Engineering, NYC Norton now manufactures and sells this beautifully fabricated component exclusively. Our kit fits all Norton twins that have a large sump screen on the bottom of the motor and installs in minutes with no permanent modifications necessary. Complete kit contains Breather, blanking plug, proper oil lines, stainless hose clamps, copper crush gasket, and instructions. Screw it in, plumb it up, and go!
No engine we build leaves our NYC Norton shop without a good breathing setup.
(Note: Certain Commandos built on or before 1971 utilize a crossover frame tube under the motor which can, on occasion, prevent installation of this breather. Please email firstname.lastname@example.org if you are unsure of compatibility)