Is it a 650 or a 600 Norton? We look into viewers comments ! 

now my bike was built way before this one back in december 7th 1960 and its a early 650 manxman built for export only and to date there are only 12 in this country thats come back a very rare machnie and a very nice looker

The difference between the 600 and 650 is primarily the stroke, a late 600 crankcase like yours will take the 650 crank and rods, so the way to tell is measure the stroke, the 600 is 82mm and the 650 89mm. So it could actually be a 650.

its REVELATION not Revulution and considering you being around this bike for a few years you would know this '63 machine would have left the factory with Monobloc(s) not concentrics as you wrongly state and the if motor is "untouched " factory spec 99ss, it is a 600 cc.

As several other commenters have pointed out the carbs are Amal Concentric. They are Mk1 though, definitely not Mk2.

I'm sure some of the 99ss models were fitted with cams, barrels and pushrods as part of some optional extras at the time so it's possible it could well be a 650

Hi guys, as you say that’s a 600 engine, though definitely an SS model. The engine number itself is on the left side of the crankcase, towards the front, just below the cylinders, followed by the model number (for a 99 model number is 14). The 650 model number is 18. The frame number is stamped vertically on the frame lug behind and below the battery case, but it can often be painted over, especially now that it doesn’t have to be checked for the MOT. It’s still a gorgeous bike! Btw, not sure but it looked in the video like there might be a little oil seeping out past the head gasket below the carbs, which are concentric amal mk 2s. After a rebuild, it’s a good idea to make sure the head nuts are tight to the correct torque settings, at 500 miles and again at intervals. These engines are like naughty kids, and need a firm hand!

The 99SS didn't have the downdraught head but a separate manifold iirc. You could buy these aftermarket too but the downdraught was the way to go. You may well have an SS frame etc. with a 600cc engine fitted but internals may well be 650SS. Check how the seat fits. It looks like at the back is the DZUS fastener and two pins at the front which is how the SS was. Great to see these old bikes running and in good condition. I loved mine but I was only 20 then, wow so long ago, several of my mates had Dommi's then, 650SS, Atlas, 500SS, 99'S, 88'S. Tritons, Gold Star in featherbed. AND the roads were smooth then!

hi guys ,, just come across your videos because I have just bought a 650ss and I thought I heard a little dissapointment when you thought it might be a 600 , don't be , I suggest joining the owners club and getting the history of the bike , there could be an interesting twist in its story They're great looking bikes and a joy to ride , whatever. 👌

Hi guys thanks for the comments, was the 650 rarer than the 600? Had fun fitting the new left hand foot rest last night which is wider than the old one, so now the brake pedal hits the nut.

the engine number is at the front side on the left 99ss engine number starts with 14 on the side in front of that will be your engine number 965xx a rare 99ss with concentric carberttors then not mono bloco

Look, the 650SS was basicly a 600SS with a longer stroke crank. If you want to know what it is, lift the head off measure the stroke. I suspect you could just drop a 650SS crank into a 600SS motor and you are good. Maby the factory did this, maby some guy like me in my garage. The carbs on your bike are Mk1 concentric not Monoblock. That tells you nothing. As Monoblock wore out you automaticly replaced them with Concentric which were easier to adjust. I run 2 nortons, a concours 650SS 1963 and A 1964 750 . Café racer production race tuned. The Norton motor is simple and it is easy to swap parts between models. Let me give you an example. I took a 1949 Model 7 500cc that was rusting in a garden, dropped in a 750 crank, 750 barrels, sphered and gas flowed the head out to 32mm carbs. Nobody could understand how a 1949 500cc bike could drag the lights against Japanese 4s

Could be a 650 top end

and its not a 1963 ether london reg 1962 the easy way of telling the model is the model number stamp on the side of the crank case now for 500cc featherbed you get 122 model 88 for model 99 is 14 for 650 its 18 or 18ss plumstaed built for all atlas 750 cc models its 20

600’s are faster. Tongue in cheek.

99 is a 600cc