Topic: '73 Norton bottom end overhaul  (Read 321 times)

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Offline norton73

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« 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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« 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;

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Offline norton73

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« 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

Online Fencejumper09

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« 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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« 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'!

Offline norton73

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« Reply #5 on: September 13, 2017, 04:40:39 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!

Yeah, sucks about Gary.
We left the rally shortly after he did, but we went SW to visit my wife's parents after the rally. Otherwise, we'd have driven home the same way he went and been able to pick him up with the trailer and bring him home.
Too bad RJ doesn't have bike hauling capabilities with that rig.



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Offline norton73

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« Reply #6 on: September 13, 2017, 04:44:23 PM »
While the wife's at work, the mice will play....


Had a little distraction last week, so didn't make any progress on the Norton.

Decided to clean up the cases in preparation of painting them;



Blew them dry with compressed air, then finished the job with the oven;



it needed cleaning anyway...

 :)
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Offline kdtrull

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« Reply #7 on: September 13, 2017, 05:43:09 PM »
That'd get you a good whoopin' in Lisa-land.   ;D

Offline renchinrider

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« Reply #8 on: September 14, 2017, 10:10:20 PM »
 ;D ;D ;D
Live to Ride...or Die Tryin'!

Online springer

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« Reply #9 on: September 14, 2017, 10:50:14 PM »
 BEST use of an oven EVER! ;D

Offline dredman

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« Reply #10 on: September 14, 2017, 11:08:16 PM »
Lynn does not log in?  Watch over your shoulder?

What she does not know will not hurt  8)

Offline dredman

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« Reply #11 on: September 14, 2017, 11:09:38 PM »
Never mind, I remember you can ride the trials bike in the bedroom  ;D

Offline Chitza

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« Reply #12 on: September 15, 2017, 12:19:03 AM »
BEST use of an oven EVER! ;D
Only because you have never eaten my Thanksgiving Dinner. But I will accept it's the SECOND best use of an oven.
Loud pipes make me hungry for Valium biscuits and scotch gravy. - kdtrull

Yeah....ham it up, crackers.   ;D -kdtrull
The politically correct term is "Saltine American". -KevinB

Offline norton73

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« Reply #13 on: September 15, 2017, 06:37:22 AM »
BEST use of an oven EVER! ;D

I'm not done with the oven yet.

More to come this weekend.
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Offline norton73

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« Reply #14 on: September 18, 2017, 09:08:59 PM »
Found a little time on the weekend to continue with the work.  Threw the cases back in the oven and the main bearing outer races in the freezer;



They dropped straight in with no issues. I then assembled the cases with the crank and measured end play again;





end play is 0.012, same as when I disassembled it. Spec is 0.005-0.015 to allow for expansion. I've heard some racers go as much as 0.025 or more.

Checking the clearance in the cam tunnel for the fancy new high lift cam.



Then I painted the cases. I used the gaskets as a pattern to mask off the places I didn't want paint.





Several coats of BBQ silver later;




Loose nut holding the handlebars