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1973 Norton Main bearings

Classic Norton Commando Motorcycles.

Re: 1973 Norton Main bearings

Postby norton73 » Sat Aug 12, 2017 6:18 pm

acadian wrote:
norton73 wrote: the inner main race on the primary side turns by hand on the crank. Can't pull it off by hand, but will spin.


if the inner race spins on the journal, bearing not doing its job... no?



Good point.


I don't see any blueing or any sign to my eyes that the bearing locked up or wasn't spinning. Only that the inner race is loose.

Most likely I'll put new bearings in, bike has 65k + miles.
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Re: 1973 Norton Main bearings

Postby Dances with Shrapnel » Sat Aug 12, 2017 8:18 pm

pommie john wrote:
norton73 wrote:......... Maybe reuse and red locktite the race to the crank and reassemble with new rod insets and go from there



Loctite make specific products to secure bearings onto shafts.

http://www.loctite.com.au/3320_AUE_HTML ... 2648195073


What pommie john says but I would bump it up to Loctite 680. It has a high temperature rating and and is listed as best for this application. I used this on a billet crank on my 570 Ultra Short Stroke. My first showing at a track with the new build and after a few practice sessions I was getting a nasty clunking sound; especially when returning in the paddock. Upon tear down and inspection the drive side inner race was a really nice slip fit. I thoroughly cleaned bother surface, used the 680 Loctite and it lasted until we needed to replace the bearings after a season due to failed steel cage.

Since you are contemplating a hotter cam, consider a new Steve Maney Crank and your main bearing problems are solved! Not wanting to have the crank just sit there underutilized, consider some light weight pistons and rods and perhaps a Fullauto head with some Jim Comstock headwork and bigger valves. Now at this point you will need the Steve Maney racing crankcases and might as well throw in an alloy barrel to look sharp.
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Re: 1973 Norton Main bearings

Postby Dances with Shrapnel » Sat Aug 12, 2017 8:18 pm

pommie john wrote:
norton73 wrote:......... Maybe reuse and red locktite the race to the crank and reassemble with new rod insets and go from there



Loctite make specific products to secure bearings onto shafts.

http://www.loctite.com.au/3320_AUE_HTML ... 2648195073


What pommie john says but I would bump it up to Loctite 680. It has a high temperature rating and and is listed as best for this application. I used this on a billet crank on my 750 Ultra Short Stroke. My first showing at a track with the new build and after a few practice sessions I was getting a nasty clunking sound; especially when returning in the paddock. Upon tear down and inspection the drive side inner race was a really nice slip fit. I thoroughly cleaned bother surface, used the 680 Loctite and it lasted until we needed to replace the bearings after a season due to failed steel cage.

Since you are contemplating a hotter cam, consider a new Steve Maney Crank and your main bearing problems are solved! Not wanting to have the crank just sit there underutilized, consider some light weight pistons and rods and perhaps a Fullauto head with some Jim Comstock headwork and bigger valves. Now at this point you will need the Steve Maney racing crankcases and might as well throw in an alloy barrel to look sharp.
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