Sorry it has taken me so long to respond to your request. I have not touched a motorcycle in 40 years, sense I left Norton, so I had to wait for my brother to retrieve some of my old notebooks held in storage all these years. Unfortunately acid paper, disappearing ink, moisture and boxes that could not be found, will limit my response. I used to keep detailed notes on many of the projects and technical back office discussions.
Trying to follow the various treads seemed to reveal several questions that I will try to respond to in no order. But I will try to focus on the Cycle Dec 1972 Superbike comparison. Let me start by saying that to my recollection, we (NVL) were not all that please with the article’s edited form, but felt OK about the Norton’s overall placing based solely on the graded values, although they could have been better.
I was in England when the 1970 comparison test was done, but there was a deep concern about the “cheating” tone that existed during that get-together. So it was determined that the Norton Roadster for this test was to be exactly what a customer would drive off the dealers showroom for all aspects of the testing. NVL was not known for extravagant expenditures, so we did not pull a brand new 1972/73 bike out of the create to use. This Combat Roadster was our demo bike that we had been using as a loaner to magazines, testing the latest upgrades and engineering changes (EC’s) to support our dealer network.
The Commando generated about 45 to 70 upgrades and EC’s a year so before we gave the bike to Cycle, I had to clean and blueprint the entire bike to what was current from front to back. From the picture in the article you will see the black cylinder barrel, so we know it was the combat engine. I could not find the serial number to verify what was in the crankcase, as that was the only part of the bike I did not dig into. The bike was prepped in October 1972, so everything available at that point in time was in or on the bike. Cycle also just published the 750 specs from the sales brochure, except for the Torque and HP numbers that they used from their dyno test. This bike would not have had a 10:1 compression, as I was not using a cylinder base gasket and always used the copper head gasket. Most likely it was the 1mm copper gasket, so the compression would have been 9:1.. not the 10:1 designed for the 2S cam. A note on the cam and main bearings.. we had 3 cams floating around in 72 and 2 sets of main bearings. A standard ‘Atlas’ 750; Combat 750 soft grind, and the Combat grind both known as the 2S grind. The soft grind was a manufacturing error that caused the cam to wear, we had many of those wielded and reground. So to all questioning the cam.. assume it was a Used, NOT worn, 2S. Cycle did not publish the open/close timing specs for the teardown inspection, nor do I have Axtel’s dyno printouts to compare with the Cycle published graphs. The Axtel dyno output graphs for cam tests that I had, are now just blank pieces of paper. Bottom line.. it was the Combat 2S cam in that test bike, set to factory spec. I found no reference to the main bearings used.
The way the article was laid out also differed from the actual test sequence as I remember it. I seem to recollect that the 1st day was the basic run-in and decibel test day. We had some issues that day before we could turn over the bike. The first was a weak spark issue that caused plug fouling. The sentence about “thrashed on the Norton” came from me feverously trying to track down the fault. I ended up bypassing the Ballast resistor to fix the problem. We also dropped the jetting and played with the needle position because of weather conditions that day. The other issue that day was the Norton failing the decibel levels. The mufflers on the early combats had a baffle that caused a whistling at a high frequency that put us over the limit. Brian Slark fixed that by taking a long screwdriver and punching out the baffle, allowing the Norton to pass the test.
Once we turned the bike over to the Cycle guys, we never touched the bike again, so it ran with the leaner jet and the punched out baffles for all remainder testing. Also, because the decision was to use a spec Roadster it would have had the 19 tooth drive sprocket rather than changing to the Interstate 21T for the drag tests. The other two issues mentioned in the article were the clutch slippage and sputtering at high speed. The clutch I would attribute to putting in the new solid metal clutch plates and the other to Amal carb issues with foaming petrol in the float bowl or the small jet restricting gas flow. I think we would have done better with the drag and dyno tests if we played a little with the settings, pushing us up a slot in the standings… The Norm White drag run was a brand new 73 Combat with factory settings, it produced 12.24 sec 1/4 mile... I hope this helps.
