1975 MkIII Long-term Rebuild

After posting a picture of a project bike that I picked up last summer, I decided to start a new thread about it. The bike is a 1975 Norton Commando MkIII that was last on the road in 1983. Most of it is in boxes, and everything needs going through to see what is serviceable and what needs to be repaired or replaced.

The prior owner said that it was a bad cam that caused it to be parked in 1983. He started a rebuild back then, but never finished, and the bike sat dormant in his basement. The first picture is of the bike loaded on my trailer. We were going through the boxes to see what was there.

While I have done a good portion of the maintenance on my 1970 Commando over the years, I have sent larger jobs out to 'specialists', for better or worse. I am trying to do as much as possible myself on this one, so it will be a slow slog as I learn a bit more about these machines.

looks promising so far, enjoy

Good luck! If you can work on a lawn mower you can work on a Norton.

Thank you for the well wishes on the project.



The first step after getting the bike home was pulling the bottom end from the MkIII chassis. It is interesting to see the differences in the e-start primary compared to the earlier machines like my '70. Everything looked pretty clean for a machine that has sat for 40 years, though there was a bit of rust on the clutch diaphragm.



With the engine out, I took a pause for a bit, as I did not have the proper timing pinion extractor. A friend who had one graciously offered to help with dismantling the timing side of the motor. With his help, the timing side was taken down and the cases split. Everything came apart relatively easily. I still need to do some clean-up and order up a few parts, but I now have a good starting point for the rebuild.

A bit of ugly. It looks like the original rebuild undertaken on the bike made it as far as replacing the camshaft and reassembling the cases. A look at the followers shows that the wear on the right intake looks like it might be too deep for resurfacing. New cam followers are in order.

Looks very clean inside. I'd plan on replacing the cam. I think Web cam or Mega cam will re-hard surface the lifters, cheaper then buying new!

rightshiftrick said:

A bit of ugly. It looks like the original rebuild undertaken on the bike made it as far as replacing the camshaft and reassembling the cases. A look at the followers shows that the wear on the right intake looks like it might be too deep for resurfacing. New cam followers are in order.

Click to expand...

Weird, 3 tappets with almost no wear and one gone! Better check how well they move in the cylinders - might need cylinders

Broken safety wire is also a concern.

marshg246 said:

Weird, 3 tappets with almost no wear and one gone! Better check how well then move in the cylinders - might need cylinders

Broken safety wire is also a concern.

Click to expand...

Thanks,

I still need to check over and measure everything. This was a bit disappointing to see, but I am sure not the last issue. I will find.

RSR

Megacycle 560-00 cam and have them radius the lifters to match. Definitely replace the dented one.

You could put a JS Motorsports JS0, JS1, or JS2 cam in it and still enjoy the motor on the street. All that needs to be done is radius the stock lifters. JS will do the radius work with your stock lifters. Link to some info. Follow the directions, but for the most part the JS cams install just like a stock cam and the stock push rods can be used.