1973 Mk1 Rebuild, back from the grave!

Tony Pierce

Tony Pierce

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Mar 7, 2019
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First off, I'd like to thank everyone for the wealth of knowledge on this forum. I have built or modified quite a few bikes in the past (Ducati, Yamaha, Honda, Triumph) but never a Norton.

My father in law came in from out of town about a week ago, bearing gifts from Arizona. With him in the back of his truck was a Norton Commando, purchased in 1974 as new (build date on frame is June 1973). He rode it for a few years, but it has essentially been sitting for close to 40 years.

It is in pretty rough shape, but it is a labor of love. I really enjoy working on motorcycles, and I can't wait to see the look on my father in law's face when it is finished. Although he gifted it to me, this is something I will keep forever and cherish. In it's current condition many people might have just parted it out, but I think under the patina there is great potential.




 
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I plan on doing a complete frame off restoration on the motorcycle. When I went to split the primary drive I was surprised how good everything looked. Chain was good, clutch looked great.

 
I pulled the motor out last night, and removed the head and bores. I will need to bore out the cylinders and install new pistons and rings. I also plan on rebuilding the head in installing new crank bearings, although that is probably not required. The motorcycle only has 6500 original miles on it.

Is there a consensus on the best bang for buck on pistons and rings? I need to place an order soon.




 
EMGO pistons, Hastings rings. Reasonable cost and proven performance. Your cam looks in good shape. You made the right decision. That bike was way too nice to part out even if the outside is a little crusty. That primary looks like new.
 
The gutty works look very nice. Some TLC and that's going to become a jewel. Wish I had your opportunity.

That's not rough...only well seasoned.
 
Thanks for the comments! I ordered the pistons and rings and will contact a machinist on Monday for the jug machine work. I have plenty to keep me busy until I get them back!
 
I have contacted Mr. Comstock as suggested, and he is machining out the cylinders for me soon. Just crated them up and will ship them to him tomorrow. He has his work cut out for him, I managed to slip and chip a fin! Bummer!



I worked today for a while cleaning the heads up. Once I get the cylinder back I will ship out the head for refurbishment as well. It doesn't have many miles on it, but I want to do things right. I will end up replacing valves, springs, and guides I think. For some reason the exhaust rings absolutely refused to come off. The exhaust was trashed, so I ended up just cutting it off and will have the head shipped out for machine work with the rings- hopefully he can remove it ok. I was afraid of breaking something after destroying the spanner I purchased (Andover Norton).
 
Keep on plugging & you'll get it...I believe my top end is coming down maybe this next fall for a long overdue inspection. Mainly because of an oil leak starting between the head & jug at the push rod tunnel. Not side tracking your thread, just wanting you to not feel all alone in the dark.

I hope mine stops there though.
 
Thanks CJ!

I am contemplating opening the cases and replacing the connecting rod bearings even though they "feel" good, because I have the top end of motor already open. Are the rod bolts reusable? The engine has never been apart and has around 6500 miles on it. Any other "must dos" while when I tackle the bottom end?

I have already bought the layshaft bearing for the transmission, as well as the seals and gaskets needed, so I will tackle that after a while as well.
 
I would leave the crank and rods as-is. Commando 850 bottom ends are pretty strong. You can pop the drive side case off, put in a new seal and clean things out if you want before re-assembly. The unmolested crank and rods can remain in the timing side case. As clean as the top is, I can't foresee any bottom end issues. As long as the crank and rods rotate smoothly and the cam looks ok, it shouldn't be necessary to break everything down to parts. Lots of miles to go before those rod and main bearings need replacement.
 
Think I'd clean out well, do a careful visual, lube, & go with it also. Would go over the oil pump too for a grin to see what there is to see.
 
I can only go by my personal experience of looking at old motorcycle rod bearings and not one to date am I regretful of checking and replacing which would be all. :D

There is also the possibility that if sitting for 40 years, oil left in that location has become toxic to the shell surface and that the main bearing elements have left microscopic marks where they rest against the races.
What is a weekend to check compared to the 40 years the bike has patiently been waiting. ?

PS... The connecting rod rotating smoothly tells you little about the shell or journal surface, all it might need is the journal getting a quick polish and a new set of shells along with a running clearance check.
 
Time Warp said:
I can only go by my personal experience of looking at old motorcycle rod bearings and not one to date am I regretful of checking and replacing which would be all. :D

There is also the possibility that if sitting for 40 years, oil left in that location has become toxic to the shell surface and that the main bearing elements have left microscopic marks where they rest against the races.
What is a weekend to check compared to the 40 years the bike has patiently been waiting. ?

PS... The connecting rod rotating smoothly tells you little about the shell or journal surface, all it might need is the journal getting a quick polish and a new set of shells along with a running clearance check.
Click to expand...

Thanks for the advice. I had already bought the bearings and gaskets/seals needed so it would not cost much more than time at this point. Do you suggest replacing rod bolts or just the nuts? The bolts seem incredibly expensive for top shelf units and the torque setting is low enough I would be surprised if they fail due to stretch. But it's not worth gambling a few hundred dollars over if people have had failures due to reuse.
 
Is that a Hodaka Ace 100 ?

Yes you can get away with changing the nuts only as posted already.

I think as long as you are careful and put each stud and nut back in the exact same location ... ie The stud going left to right as removed and nut on the stud end it came from in the same configuration it is OK to reuse the hardware that holds the crankshaft cheeks to the central flywheel also.

I was not overly impressed by the modern kits anyway compared to the original parts.
 
On the note of opening the bottom I'll have to go ahead and agree if it really has just been sitting for forty years because there'll be a varnish-like layer more than likely from oil drying out. I didn't just let mine sit in stasis for close to that period(38), rather it was kicked over a dozen or more times each month to keep everything moving well and even some oil moved around a bit being concerned over locking up. Time Warp has given the most sound advice.
Magnaflux the bolts would be nice if you reuse for insurance.
 
Tony Pierce said:
Wow good eye! That was my first motorcycle at age 9. I saved up mowing lawns, shoveling snow, and splitting wood for 2 years for that bike!
Click to expand...

My beginnings were in the dirt with a brand new Suzuki RM125S model in August 1976, aged 16 and a boilermaker/welder apprentice on $30 per week and a $300 deposit, it was the factory 'hop up model with low pipe, 34 mm VM and uprated cylinder, a fairly rapid learning curve being the first motorcycle I had ridden.
I still have most of it in boxes (along with a couple of spare engines)

Keep up the good work.
 
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