1967 Norton Atlas main bearings

You should remove the shields & wash out the grease, as the engine oil will provide the lubrication.
 
Well I'm at a point where everything is about to go back together. I have both FAG NJ306 E's rollers (two of them) and a Timken /Fafnir 306W ball bearing with 10 balls. if I understand this correctly, using the ball on the time side does not require any crank shimming as supposedly once the nut on the crank is tightened it places the crank where it needs to be and then the roller goes on the drive side. if I opt for two NJ306 rollers then I need to check the end float. In this scenario what would the Max/ Min end float want to be? Interesting when you go on the RGM site and click on a .003 shim, Roger makes a statement that end float on these engines is not all that important?
 
A far as I am concerned Roger is correct for a street bike engine that isn't going to see extreme RPM for extended periods of time. Even if it did, I'm not sure how important end float really is as long as it is somewhere within the rather broad spec that has been mentioned in the Commando forum a few times recently. Somebody is going to disagree without a doubt.

Of the 5 times I've done my 750 engine top to bottom trying out different configurations, I only checked crank end float when I put a new Molnar crank in the cases. Turned out I didn't need to shim it, but I did have .003 shims just in case it was too sloppy. I've never lost a crank or set of main bearings in said 750 engine, but it is a street bike, and I don't have that many miles on the Molnar crank and new set of roller mains.
 
Hmm interesting Schwany. Just out of curiosity what have you done in the past roller / ball or roller/ roller?
 
jms said:
Hmm interesting Schwany. Just out of curiosity what have you done in the past roller / ball or roller/ roller?
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I switched to roller mains the 3rd teardown and rebuild in the 1990's. My philosophy was at that time and still is today if it is good enough for a Commando it's good enough for a pre-Commando. I figured it would make the bottom end stronger.
 
Update. So i assembled a dry run and measured the end float which was 20 thou. Now I'm aware of all of the different opinions on how much is too much and how much is too little. I've got four .003 shims so I could bring it down to 14 thou or 8 thou. In peoples opinion which should it be?
 
No takers I see on my last question Hahah. How about this question, when shimming a crank how important is it to shim equally on each side?
 
jms said:
No takers I see on my last question Hahah. How about this question, when shimming a crank how important is it to shim equally on each side?
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Shim the crank so the rod small ends are centered in the cylinder bores.

If you're using two rollers, shim to the end float spec of a Norton motor that was spec'd with two rollers.

Do you not have any workshop manuals?
 
t ingermanson said:
Shim the crank so the rod small ends are centered in the cylinder bores.

If you're using two rollers, shim to the end float spec of a Norton motor that was spec'd with two rollers.

Do you not have any workshop manuals?
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I have theb
t ingermanson said:
Shim the crank so the rod small ends are centered in the cylinder bores.

If you're using two rollers, shim to the end float spec of a Norton motor that was spec'd with two rollers.

Do you not have any workshop manuals?
Click to expand...
Thanks. I have the manual for the 71 forward Commando but not the Atlas. Need to get one. Just wasn’t sure how much of the Commando manual applies
 
I would leave 20 thou alone, the later Commando max was nearly 30 thou. Last one I worked on was at 30, I only added a 10 thou shim on the drive side as there was evidence the crank web was touching the drive side crankcase at high revs when the crank bent.
 
jms said:
Update. So i assembled a dry run and measured the end float which was 20 thou. Now I'm aware of all of the different opinions on how much is too much and how much is too little. I've got four .003 shims so I could bring it down to 14 thou or 8 thou. In peoples opinion which should it be?
Click to expand...

0.020" is fine and using the shims that AN supply is not a good idea and even worse if used stacked up only coming in 0.003".
One selective shim only under the main bearings (if excessive end float) in my opinion.
 
Time Warp said:
0.020" is fine and using the shims that AN supply is not a good idea and even worse if used stacked up only coming in 0.003".
One selective shim only under the main bearings (if excessive end float) in my opinion.
Click to expand...
actually these came from RGM but the same approach up against the crank cheek
 
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As the large which fit under the roller bearing are not anymore available from Norton suppliers (old Brits had them before ..) , may be you could find some there ?
 
jms said:
actually these came from RGM but the same approach up against the crank cheek
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I assume you wouldn’t use the AN shims because they run the risk of getting ground up?
 
jms said:
I assume you wouldn’t use the AN shims because they run the risk of getting ground up?
Click to expand...

Most folk do not have the means to shim the crankshaft easily and the resellers (Besides Old Britts when they sold the shims to go under the bearing outer) seem to be stuck in the 1970's with those crappy cheek shims which would be a total pita to fit.
Jim Comstock posted in the past that they could move and cause problems, that was good enough for me.

I simply machined dummy bearings so it could all be done with bare engine cases (not needing to remove new parts to place any shims) then machined stainless steel shims to suit in a lathe fixture that clamps multiple blanks which then can be faced for the OD and bored for the ID.
That OD and ID is what I deemed suitable. (The start end float was 0.031" with the original cracked crankshaft and 0.029" with the replacement crankshaft on my 850.
(There is a possibility the drag from the oil pump would push the crankshaft away anyway via the drive gear angle)

If the engine has 0.020" with the new parts it would be fine, if you wanted a project, you would only be chasing 0.005" or so which I would be tempted to not bother with.

1967 Norton Atlas main bearings
 
jms said:
No takers I see on my last question Hahah. How about this question, when shimming a crank how important is it to shim equally on each side?
Click to expand...

I milled the top off an old piston to see where the rod sat, there was miles of clearance each side and central enough.
I shimmed under each bearing outer equally simply to have the minimum stick out from the engine case bore on each.

It was only an 0.008"inch or so reduction overall down to around 0.012".
In your case of 0.020" down to say 0.012" / 0.015" that would hardly be worth the effort on a road bike and about right for a race bike (according to Jim Comstock.
He posted minimum 0.010" for a road bike (I went higher to 0.012"/0.013") and minimum 0.020" on a race bike.
 
Time Warp said:
I milled the top off an old piston to see where the rod sat, there was miles of clearance each side and central enough.
I shimmed under each bearing outer equally simply to have the minimum stick out from the engine case bore on each.

It was only an 0.008"inch or so reduction overall down to around 0.012".
In your case of 0.020" down to say 0.012" / 0.015" that would hardly be worth the effort on a road bike and about right for a race bike (according to Jim Comstock.
He posted minimum 0.010" for a road bike (I went higher to 0.012"/0.013") and minimum 0.020" on a race bike.
Click to expand...
All great info. Thanks
 
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