Piston ring sizes – I rarely work on bikes these days, the parts business keeps me hopping. However I have a couple of times recently told customers wanting piston rings to take the next size up if the size they want is out of stock. Had a guy today needing +30 for his Commando so I told him to use +40’s and carefully file the end down to get the optimum gap (4 thou per inch of bore). Wouldn’t do it “because the tension would be wrong”. Well I did it many times in the 60’s and 70’s and never had a problem – I actually preferred it with a slightly worn motor.
The spoke bend angle keeps raising its ugly head. I’ll say it again, if adjusting the bends of our spoke sets by 5 to 10 degrees when you fit them is not your thing, please buy your spokes somewhere else, and in the words of our UK manufacturer “you should not be trying to build a wheel”. Of course if you send me specimen spokes to copy I’ll get them made exactly for you, but they will be slightly more expensive.
OK it’s not quite stock – some of you will have noticed that the Amals have been replaced by a single Mikuni
Customer with 1965 650 Twin thinks his motor is not original because his frame is stamped A50****
BSA didn’t start matching engine and frame numbers until part way through the 1966 model year. All 500 & 650 A50 & A65 variants up to that time had frame numbers starting with A50.
Roy Bacon’s BSA Twin and his other restoration series books have excellent information charts in them covering engine and frame numbers.
I am quite often asked how to remove the tumbler and key assembly (Lucas no 54335169) fitted to the common Lucas 2 and 4 position switches used on most bikes from the 1960’s onwards.
In the body of the switch you will see a small hole. Turn the key to the on position, which lines up with this hole, and you will see a small spring loaded brass pin in the end of the tumbler. Carefully push a thin steel rod (the back of a drill bit works) into the hole, depress the pin and the tumbler assembly can be withdrawn from the switch body.
What if the key has been lost? You will have to very carefully drill a hole in the body to line up with the position of the key, and gain access to the pin. Grease on the drill bit will reduce the chance of little metal shavings getting into the switch.
In regard to these switches, I can’t recall anyone ever having a problem with the 2 position types, unlike the 4 position ones (fitted to 71-2 Triumph & BSA Twins and 71 onwards Commando’s). With the 4 position switches, that’s the first place to look if you are experiencing any kind of intermittent electrical faults.
Here’s a story a customer sent me…..
“I remember one time I wired an aftermarket horn up on the bike because it didn’t have one when I bought it. The first time I had occasion to use it on the highway, the bike stalled because of an inherent wiring fault. I pulled over and as I slowed onto the shoulder smoke began rolling out from under the seat.
As I got off the bike to see what was the matter I tripped over the sidestand, fell over and sprained my wrist upon landing. By then there was a fire raging under the seat, so I quickly went to push the bike over close to water-filled ditch where I’d hoped to mitigate things. The front wheel fell off, which knocked the bike over, spilling gasoline from the tank all over the place; what did not ignite flooded the ditch and killed untold numbers of little frogs, poisoned waterfowl, etc.
Eventually the police showed up. Surveying the pile of twisted, smoldering metal that was once a motorcycle, the officer wrote me a ticket for littering and referred me to state agencies for pollution.
The tow truck driver charged me $90 to tow the remains to my house 5 miles, and when he kicked it off the bed of his truck the bars caught on the side, it swung around and broke the steering head off. Not that it mattered by then.
I entered the house, explained to my wife what had happened and she looked at me in disgust. Without nary a word she went upstairs, packed a bag, and left. My dog, who was a steadfast ally for years, hanged himself off the front porch on his leash.
My boss, upon hearing of this in the paper, fired me. I was forced to sell my house shortly thereafter, and ever since then I’ve been living in a homeless shelter, relying on the generosity of strangers.
Oh, if I’d only used original specification components, none of this would have begotten me.”
People seem think that I am some kind of expert on these machines and while I have owned over 100 of them over the years I am the first to admit that there’s a lot about them I don’t know. Some 10,000 machines were made using the Norton Atlas motor in Matchless/AJS frames (more than the total production of actual Norton Atlas bikes) with a mixture of Norton and Matchless wheels, frames and other parts. The series started with the Norton Atlas Scrambler in 1963 right through to the Norton Ranger (the final P11 variant) in 1968. Other machines in the series included AJS models 33 & 33CSR, G15Mk2, G15CSR, G15CS, N15CS, P11, P11A & P11A Ranger. All the P11’s apart from the final Norton Rangers were sold as Norton or Matchless models.
One thing to be clear about is these were specific models built to specifications and were not, as commonly rumoured, randomly assembled from left over parts at the factory.
There are a couple of guys in the UK, my friends Anthony Curzon and Paul Morin, who are way more knowledgeable than me on this subject.
The Atlas motor, especially the early ones, as Paul Morin once observed, got its name from the Atlas missile because of it’s propensity for blowing up. Later motors (identified by “P” stamped at the end of the serial number) were re-engineered at the Matchless Plumstead, London factory and were much more robust. Without this development work I doubt very much that the Commando (using the same motor) would have even existed.
All these bikes, without exception, had matching engine and frame numbers. The motor number had the model designation in front of it, followed by six numbers. Only these six numbers would be stamped on the frame.
I recently had an enquiry from a customer with a non-matching N15CS model. His engine number started “20/”. This type of stamping would be unique to the Norton Atlas so the engine must have been changed. It is important to note that the motor fitted to the Atlas differed from that in the hybrids. For the latter there is a raised casting in the left hand crankcase to locate the inner alloy primary chaincase and thereby precisely position the alternator stator, which is located in the outer cover. For the Atlas the stator is mounted on an alloy casting which is attached to the crankcase (just like an A65 BSA) and it is easy to make sure rotor to stator clearance is OK before fitting the outer tin cover. I am not sure that the stator would be positioned properly in his bike although I suppose patiently assembling and checking with plastigage would work.