1957 Norton 99

I watched a few of this fellow's videos awhile back. I couldn't figure out how a 99 could be capable of such great acceleration.
A few years ago I rode a restored 99 and it was, to be kind, sedate. It made my BSA Super Rocket seem like a Rocket, possibly even a Super Rocket.
Anyway, after much prodding in the comments section, the owner finally showed us the bike. It is a 1957 99 with a 750 Commando engine in place. So an upgrade from a claimed 31 bhp to a claimed 58 bhp.
Judging by the sound, it is well tuned. I'm not sure if is a stock motor or not. I would guess that he has the gearing kept low from the strong sound on shifting.
Our weather is getting good again, above 50 f and dry.
Watching this video has me pining to get out there.

That was fun!! Where was it filmed.

It's filmed in the Harz Mountains in Germany.

Glen

Glen running a Commando motor in a Featherbed frame the crank has to be balanced to run smooth with the hard mounts 750 or 850, if they aren't balanced the vibrations would be unbearable to ride, this guy has quite a few videos with this bike and I love watching them, as you say its well tuned and smooth by the looks of things with the Featherbed frame, they handle great and a fun bike to ride, I say he has built it right.
One of the reasons I love my hot 850 in the 1957 Wideline Featherbed, it's shorter than a Commando frame and so much lighter, well the Featherbed frame is heavier than a Commando frame, but you can build the whole bike so much lighter, the hard mounts with engine and GB all becomes part of the frame and one of the reason Featherbed frames handle so well.
About 35 years ago I was at my local Norton parts shop (BJs in Brisbane) I pulled up on my 850 Featherbed and there was a bloke outside when I pulled up he was all over my Norton, he knew what it was and asked how the vibrations where, I said smooth as, he then told me he has built a 750 Commando into a Featherbed and the vibrations were so bad he couldn't ride it too far, I asked him if he got his crank balanced for the Featherbed and he said he just mounted a stock 750 Commando motor, I said straight away, there is your problem.
Mine is at 72% balance factor and is just right and sounds and runs very much the same as this Norton in the video.
Some lovely roads he has to ride on the, the 66 were 600 motors stock me thinks (so a bit under powered) as when I brought my 57 Featherbed frame was - the motor/GB/Primary.

Ashley

He blurred out the speedo

I believe the Commando frame complete (with isolastics and rear swing arm) weighs more than the complete Featherbed frame.

One of the members had both types of frame on hand and weighed them on a hanging scale. The results were-

Commando – Some sort of 750, I think. No IDBare Frame: 28.5lbsFrame and Swingarm: 36.5lbsFrame, Swingarm and Isolastic Plates: 49.0lbs

Featherbed – 1955Bare Frame: 32.5lbsFrame and Swingarm: 40.0lbsFrame, Swingarm and Engine Plates: 43.0 lbs.


So just six pounds more for the Commando setup with Isos, a little less than I would have guessed.
Six pounds wouldn't make a measurable difference to handling or acceleration. It is an important 6 pounds though as it pretty much does away with vibration above 3000 rpm.

If the Commando plates and isos are made in alloy, then you can have the best of both worlds, light weight and smooth operation. Iirc the switch to alloy shaves about 9 or 10 pounds from the Commando.

Side-note- almost all of the fairly aggressive riding in the video is done between 3500rpm and 5500 rpm with just a couple of milliseconds at 6000 rpm.
So much for needing to rev to 7 or 8k, for road riding at least.

Glen

How often does anyone take their Norton to 7 to 8k RPMs for a road going Norton, even with my hot motor that would be very rare and if I did it only be a rev out from 2nd and 3rd gear before putting it into top gear, my 850 is a quick revere with the cam and port work as well open exhaust and its built to get best performance at 4k to 7k rpm max, I never do those revs in top gear, its not a race bike but would do well on the track if set up for track racing, no my Norton is just a quick get up there road going bike with a bit more get up and go when needed.
But it's not just the power ratio of my 850 Featherbed it's the lightness of the whole bike compared to a Commando, I shaved a lot of weight off my Norton in its first build and even more on when I rebuilt it 15 years ago.
As for vibrations from 4k to 7k my Featherbed is pretty smooth, the old gentleman who balanced my crank knew his stuff and he knew what was needed to be done for my 850 motor to run smooth with solid mounting plates, so I was lucky there, that was back in 1980, Ivan Tighe my cam builder put me onto him.
In 42+ years I have only lost 2 nuts off my Norton the top gear box bolt nut and one nut off my left hand muffler mount, not bad for a bike that suppose to have assess vibrations.

Ashley