05/05/2026
One of my bikes came back in for service a couple weeks back and a fifty year old factory warranty repair on behalf of Donn's Classic Motorcycles.
Purchased this bike as a low mileage original MK3 out of the USA with 250 genuine miles on it. I've always wanted a brand new Mk3 to put into my collection and I guess this was the closest I'd got to one a few years back so secured it.
Bike was eventually brought onto the bench in the DCM workshop to go over recommission. Upon starting there was an oil leak coming front of cylinders. Thinking it may be coming from one of the mounting studs, but no, further investigation was coming from a pin hole in the cylinder itself. A fault in the casting.
Only cure for this was to lift head and cylinder and "pinpoint" exactly where it was coming from. Blocking off tappet or, cam follower for some, and filling with white spirits and using air gun from outside revealed air bubbles inside the tunnel. A repair was performed and motor put back together and bike ridden around the block and put away. Problem solved.
Then sometime later it was spotted in the corner of the showroom by a customer who came to look at other MK3's. A deal was reluctantly struck as it really wasn't for sale.
However full disclosure was made of the oil leak and subsequent repair.
Off goes proud new owner with a virtually brand new mk3 with less than 270 miles on it.
Time passes and bike is sparingly used slowly clocking up mileage, leak free. Bike was ridden to the New Zealand Norton Owners Club rally where the same oil leak started to appear once again. The bike still gains the Best Overall Norton prize.
But this stage it was due for a service, oil change, valve clearance check etc.
We investigated and yes, it was confirmed. Off with its head and cylinder. Options were looked and with its inaccessibility to perform a peace of mind permanent fix I opted to replace the cylinder and pistons with a NOS set I had here tucked away. No more leaks, and I can rest easy.
It was also decided to gear up as only had a 20 tooth front sprocket.
We went to a 23 and it has totally transformed the bike. I've run 23's for years on my own personal Interstate and love them. The 850's have the torque and helps eat up the miles without revving the guts out of the engine. Happy bike and happy customer.
So a couple of messages here.
Sometimes, Theres a reason why old bikes have very low miles on them.
Also, a genuine low mileage bike has tell tale signs that mileage is accurate as photos show. Theres o build up of chain l**e grease or muck build up on the inner cases and no spanner marks anywhere.
We've certainly seen some low mileage speedos but the bike itself n say otherwise.
This one is the real though. It had just over 1700 miles when it left the shop being ridden back home.
