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Norton Heavy Twins 1949-1975+ I'll share with you my observations, findings and opinions in the articles below. I hope the content makes up for the lack of glossy & flashy presentation. This page will be occasionally changed and added to, as my free time allows. David Comeau: last updated April 2021 ENGINE Norton heavy twins-Twin and single chain timing covers Norton heavy twins head evolution pictorial 1950 model 7 500cc through 75 RH-4 850 Electric Start Commando Automatic timing chain adjuster-twin chain motors Norton heavy twins cam profile survey added profiles Norton heavy twin cam hardness/softness Norton heavy twin - crank case evolution A few pictures of the timing side - from Atlas to E-Start. GEARBOX Gearbox pressure/venting hoax revealed PRIMARY/CLUTCH Easy Pull, No Drag, No Slip Commando Clutch Commando clutch packs Atlas belt drive No mod usually goes without a hitch, this one was no exception. OIL/LUBE Commando oil filter cross reference Norton oil pump & wet sumping Drawing of the Nortech mod (now out of business?) that was done to Frank D. oil pump and cover, worth doing if your pump is not up to snuff. AMR may be doing this mod now. FRAME&FITTINGS frame#s MOUNTINGS/ISO The Isolastics are of interest to me, so I have finally done a measurement of the front ISO compression rates. Front ISO rates FRONT SUSPENSION Atlas/Commando Forks WHEELS-BRAKES-TIRES f&r REAR SUSPENSION BODYWORK-tanks-seats-sidecovers-fairings Norton Fiberglass Bodywork CARBURETOR/MANIFOLDS/AIR CLEANERS IGNITIONS Boyer Exposed The Original Boyer MK III for Norton Commando-detailed analysis originally written in 1990 Boyer Evolved Norton Commando ignitions overview Updated June 2005 Coil measurements from different types and styles new Mar 2007 ELECTRICAL GENERAL Lucas RM24 3 phase power output curve 130k.jpg RM 15 specs & testing zener regulation curve E-Start cable upgrade MODEL SPECIFIC Hi-Rider 1971 through 1975 Nortons answer to the chopper.....the ugly duckling of the commando body styles 74/75 red & blue stripe on white 1975 Electric Start Commando HOT ROD NORTONS, EXTRA PERFORMANCE MODS AND EQUIPMENT, Dunstall, Gus Kuhn, Norvil, etc. Dunstall literature