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Author Topic: '73 Norton bottom end overhaul  (Read 247 times)

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Offline norton73

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'73 Norton bottom end overhaul
« on: August 26, 2017, 09:35:44 PM »
back in July, the International Norton Owner's Association was holding it's Annual Rally in Buena Vista VA.
My '73 had a faint clunking noise going on, and a leak from the primary drive. Not thinking it was anything serious, I spent the last few weeks before the rally working on Lynn's '75 Norton. with less than a week to go, I started to work on my bike, and determined the noise was probably coming from the bottom end.
I ended up taking the Ducati Monster instead of the Norton. I didn't feel too bad, as when the Monster came out, one of the magazines called it a Norton Commando for the '90s.

I started disassembling the Norton last week, looking for the noise.
First thing I did was check end play on the crank,




Looks like .012", within specs.

Ended up tearing the whole motor apart,



Once I got it all apart, I discovered the inner race on the main bearing on the primary side was loose on the crank.
Loose nut holding the handlebars

Offline norton73

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Re: '73 Norton bottom end overhaul
« Reply #1 on: August 26, 2017, 09:43:38 PM »
Ordered parts, and while waiting, I split the crank apart.



Used a punch to mark alignment of the crank halves and to make sure I asembled the flywheel right way around.



Unbolted it, bunch of oil still in it;






The center of the crank on many older bikes acts as a sludge trap. Instead of a filter, it builds up inside the crank. A lot of bikes need to be torn down at 50K or so just to clean it out. Nortons fron 72 on have a spin on filter, so there wasn't much inside. But the bike has 60K+ on it, so while it was apart I decided to clean it out.

Pulling the inner race off the crank;

Loose nut holding the handlebars

Offline norton73

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Re: '73 Norton bottom end overhaul
« Reply #2 on: August 30, 2017, 10:54:07 PM »
Parts cleaned up and ready to put back together;




Crank halves cooling off in the freezer;



While the inner races warm up in the toaster oven;



I ended up having to press one of the races on to the crank.

Because the old race was loose on the primary side, I used Locktite 680, a heat resistant version that also resists spinning. It went together tight, hopefully it will stay that way.

Then it was time to bolt the crank back together;



Loose nut holding the handlebars

Offline Fencejumper09

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Re: '73 Norton bottom end overhaul
« Reply #3 on: August 31, 2017, 08:32:02 AM »
This is really cool to see! Thanks for documenting!

Offline renchinrider

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Re: '73 Norton bottom end overhaul
« Reply #4 on: September 03, 2017, 09:57:07 PM »
So glad to see that you're able to save your engine and that you'll soon have it back up and running!  Two of my NAVMC buddies went to the Buena Vista event--one on his Norton, the other in his motor home.  The Norton rider enjoyed the trip to Buena Vista, and the week's events.  But, shortly after departing enroute home, his engine came apart, and left pieces of the case scattered along the interstate! :'(  We're all keen to see him rustle up all the parts he needs to rebuild and get his Norton back on the road too!
Live to Ride...or Die Tryin'!