Do you like riding vintage bikes but get completely tired of the bull$#!t? Yeah, me, too. That’s why I bought back my 1974 Norton 850 Commando Roadster (he says without irony).
After I sold this very Commando about 10 years ago, I’d done a couple of Velocettes (one of which I still own and love, even though it hurts me so) and enjoyed my now-sold ’58 Triumph Trophy, but between the more aged performance (or lack thereof) and lighting/reliability issues, I thought I’d step a bit forward in time and bought the Norton back.
Forgetting my emotional connection to this particular machine, the 750 and 850 Commando are perhaps the most practical, usable-in-the-modern-world classic Britbikes. They handle well, have great power, a good electrical system and a disc front brake. Most important, Isolastic rubber engine mounts quell what would otherwise be intolerable vibes from the big parallel-Twin.
The aftermarket is huge for these bikes. You can change almost everything from standard, and often these changes are even for the better… Because I ride the bike quite a bit for commuting and on long trips, I’ve made a few upgrades. By far the two most effective have been new carburetors and electronic ignition.
I prefer the stock, correct-for-period look, so I opted for the recently introduced Amal Premier Concentric carburetors (about $170 each) to replace my worn original Concentrics. The main improvements offered by Premiers are a longer-wearing hard-anodized forged aluminum slide (replacing zinc), ethanol-resistant “Stay-Up” float, and a real, changeable idle jet (standard is a pressed-in bushing). I had to swap to a richer slide cutaway than ’74 stock due to the changes in (crappy-for-carbs) modern pump gas vs. that which was offered back in the day. Replacement slides cost $37 each, but if you happen to know your tuning specs ahead of time, most dealers will provide the carburetors set up to your specification.
After careful synching, futzing around with the air screws and adjusting needle heights, carburetion is very good. Fuel consumption is in the 50-mpg range most of the time. Hard to beat and they have been completely trouble-free.
Stock Commando ignition is dual points and centrifugal mechanical advance. The system can work well and be reliable if all is in perfect shape, but the moving parts and weight-return springs are typically worn out after decades of use, leading to inconsistent performance and erratic idle. My choice to replace the analog stuff, after advice from pros, was an Australian-made Tri-Spark Classic Twin electronic ignition ($342). The red-anodized, cookie-sized unit bolts right in where the stock ignition used to be. Minor alteration to wiring retains the stock harness and look, so no one will be the wiser. The Tri-Spark offers a good advance curve and an idle-stabilization protocol that really works.
JRC Engineering imports both Amal and Tri-Spark brands. To find a dealer, visit jrceng.com.
My 850 Commando was transformed by these changes. Idle, throttle response and overall running quality are excellent. It starts first kick most times and runs without a hiccup.