A very puzzling 650 motor .

I recently got to look over a 650 bottom half that has been in storage for Decades . The crank had the alternator section missing. the normal engine breather was properly plugged . The cam was on needle rollers with oil feed at the end , The flywheel looked small . There were no normal engine numbers ,just a tiny unreadable 3 digit mark. The cam looked like it had a longer duration than std. No breathing method to be seen , No extra holes in timing side. Seems likely a factory race engine , Were there many 650 factory non proddy race bikes though ?? Dont remember reading about them.

Sounds more like a non-factory race or cafe-race engine.

Back when this motor came from ( 1960's ) Cafe Nortons were very rare , un numbered cases even rarer , The factory needed all they could make for exports Needle roller conversions were something you read about but never expected to do. Perhaps a dealers race bike , Genuine Dunstalls had engine numbers ,had to to get on the road.

norton bob said:

Cafe Nortons were very rare

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Not as rare as factory racers. That’s the only reason I doubt that you have a works racing engine: statistics.

I knew guys who were machinists and took their bike project parts to work with them. Replacing bushes with needle rollers, perhaps pointlessly, all over the bike was exactly the sort of thing they did. So was turning metal off the flywheel.

Many engineering plants had comprehensive stocks of bearings, which the workers felt entitled to steal.

Some of the blokes raced their bikes. Many just wanted a souped-up bike on the road.

Your comment was usefull as it drove me to ask the quetions . The motor came from the closure of Reg Deardons shop. Reg was the factories main outlet for pukka race bikes that were exported all over the world . When the factories own race shop was closed ,Reg got much of the shop stock of race parts. Records show that he handled around 7 of the 650 cc factory produced racers . Would be nice to get a photo of one. The PR 650 i am building has a pretty unique set of pipes (not actually correct as they were made for the later Atlas PR racers ,a few that were built in the later 1960's. I have a photo somewhere. By another strange coincidence the 650 motor in my bike shows signs of race preperation and the frame has had mods to stop the swinging arm spindle from turning and comming out. Something they were prone to if raced . If only they could speak !.

Well that might be different then.

norton bob said:

I recently got to look over a 650 bottom half that has been in storage for Decades . The crank had the alternator section missing. the normal engine breather was properly plugged . The cam was on needle rollers with oil feed at the end , The flywheel looked small . There were no normal engine numbers ,just a tiny unreadable 3 digit mark. The cam looked like it had a longer duration than std. No breathing method to be seen , No extra holes in timing side. Seems likely a factory race engine

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Please post a few pictures. I am curious about the oil feed to the camshaft.

- Knut

HI Knut , not mine !, may get the chance,

I believe the factory race 500s had that feature.