worntorn said:
One bike that scorched around the IOM was a direct ancestor to the 650ss. This was the little 500 twin that Doug Hele prepared, the one that became the first pushrod machine to lap the IOM at over 100mph. Hele used the downdraught head design of that bike for the new 650, that is were much of the extra power came in. Glen
Norton was despatching the 650 Manxman with it's downdraught head at the beginning of November 1960, so I would say that the Domiracer was the offspring of the Norton 650.
An old racer in the U.K. has a lowboy Domiracer which he has had since the 60s. It has a plain finished frame, not nickel, with no numbers on it. He has the bucket-tappet cam and the special head with it's eccentric rocker adjusters for the bike. He also has the "handed" Amal Gps and a set of the all-alloy short rods for use with the short nikasil cylinder, which have 650-size big-ends. It is the most complete lowboy Domiracer I know of with the most development parts and it has a history back to the 60s, the only such survivor I know of. It's present owner got parts right from Paul Dunstall back in the day.
Back to the 650ss. All I have left to do on my 62' to get it on the road is put the wiring back in. It will be all stock except for maybe a conversion to 12 volts. I have the stock compressioin, x1 cam, standard bore, head untouched except for a very light valve job, stock springs and original size carbs with the original sleeves still in the inlet ports. Also stock exhaust and it is running Avon Speedmaster/SM tires on the front and back as might have in the early 60s. So it should perform very close to the way they did 50 years ago, and very close to the way a stock Norton Manxman would. I will be glad to wring it out this spring and summer.
I rode a stone stock Manxman for many years, and it is still being ridden by the guy I sold it to with 20K miles on it's original cylinders, rods and pistons. John Gregory, builder of the Hogslayer Norton drag-bike which T.C. Christenson won fame on, said there was nothing wrong with the early 650/750 rods as long as the rod bolts were torqued properly, he used them in nitro-burning drag engines.
A former Norton factory employee said that the works put two complete lowboy twins together for their use. Also Rudi Thalhammer was supplied with a works twin roadracer. A few racers with Manx frames and 650 engines were put together for Luigi Taveri and Derek Minter to ride. Three works 500 twin roadracers were sent to the USA early in 1962 for distributor Berliner to use in AMA road-racing. Per AMA rules they had to be built around a production featherbed frame and off-the-shelf engine castings along with a kick-start mechanism just as the Daytona Manx Norton's had to have.
Heinz Kegler worked at the Norton experimental department from the late 50s through 1962 and was at the IOM to see the Domiracer do it's thing. He also had a 650ss development bike that was his to test that had a lot of tweaks which were meant to go into the production bike. Unfortunately when AMC shut down the works at the end of 62' the performance tweaks were lost. Heinz' 650ss had a bit hotter cam with radius lifters, 10:1 pistons and 1 1/8" monoblocs among other tweaks. He said the bike was tested at MIRA at over 125mph, and he said he had it going 200km/hr on the open road.
The 750 Norton came out for sale in the USA during 1962 and the Atlas scrambler in 1963 and the 650 was no longer a priority in the USA and that seriously cut the demand and sales of them afterwards. There are quite a few of the blue 650 Manxman bikes in the USA in various states of disrepair, and a few original and restored ones. There is also a fair number of 1962 650ss bikes in the USA, which was were most of Norton's "flagship" production went. 650ss USA imports for 1963 and later were very low. 1963 Production was very low because AMC was moving production. For some reason the 650ss kept it's small carburetors and inlet sleeves for all production except it's last year, when suddenly it was given 930 Concentrics. The 650 Mercury and it's single carburetor of the late 60s was an oddball bike which for some reason superseded the 650ss and was sold in the USA through the end of the 60s.
Functionally there is no difference between the 650 and 750 Norton engine except for the smaller cylinder bore, inlet sleeves and valves of the 650. With identical parts there is no reason the 650 should not put out close to the same power per CC as any other Norton engine. Early Triumph Bonnevilles had the same bore-size 376 Amal monoblocs as the early 650ss had, but got bigger carbs and more development than the 650ss in later years. I am sure the two are very close in performance in a straight line and the one that is in better tune would probably win the day. Of course in the twisty stuff I would rather be on the Norton.
