Author Topic: Drive side crank bearing - Roller or Ball ?.  (Read 4330 times)

Offline Josh Cox

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Drive side crank bearing - Roller or Ball ?.
« on: 04.07. 2009 00:42 »
Have just opened my crank case, am going to be changing the drive side bearing, it presently has a roller bearing.

Is there any advantage to replacing with ball bearing, lateral stability perhaps ?.

I am lead to believe the older engine originally had ball bearings then changed to roller, your thoughts ?.
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Offline trevinoz

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Re: Drive side crank bearing - Roller or Ball ?.
« Reply #1 on: 04.07. 2009 00:53 »
My thoughts on the change from ball to roller bearing is that the designer of the engine knew what he was doing.
Depending on how you use your machine, the ball may well be OK.
BSA tried the ball again in the early A65s but soon went back to roller.
I have recently seen an A65 engine that had the roller replaced with a ball bearing. The bearing was completely buggered. I have yet to see a roller as badly worn.
Trev.
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Online Brian

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Re: Drive side crank bearing - Roller or Ball ?.
« Reply #2 on: 04.07. 2009 02:43 »
Trev is right Josh, your engine definitely should have a roller bearing and I would put one back in. One thing to be a bit wary of is to make sure you get the correct lipped type bearing, a lot of modern roller bearings have plain outer races. Trev may be able to advise here but I think the correct bearing has a NF prefix to the bearing number.

As stated the A65's did go back to a ball for a little while and it was unsuccesful but I would be cautious in drawing any comparisons between the A10's and A65's. I believe, and my opinion is shared by a lot of others, that the A65's were a major step backwards for BSA. Here in South Aust the police used A10's and talking to a ex police mechanic they never had a problem with timing side bushes but the A65's were a disaster from day one. Having a shorter stroke they reved harder and with the revs came vibration and I believe it is the vibration that caused most if not all of the problems associated with A65's. (by now any A65 owners reading this will be ready to wring my neck !). However the A65's were a lot easier to work on and had alternater electrics etc. I have had A65's and A50's and have got rid of them all and now just concentrate on the A10's and A7's. I must admit the A50 was a nice bike and I often wonder if I should have kept it.
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Offline Josh Cox

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Re: Drive side crank bearing - Roller or Ball ?.
« Reply #3 on: 04.07. 2009 12:37 »
I get the message, I'll stop being a pussy and use the roller bearing.

Was trying to get around possibly destroying a bearing whilst setting up the shims.

Orabanda made an awesome suggestion that I'm going to modify for myself.

His suggestion was to machine up a fake bearing for a loose fit on the crank, put the crank together, measure the play and shim the new bearing to suit.

My idea is to take the old roller bearing, Araldite it together, dremel the ID and OD down a little for easy fit and remove, then measure the required shims with the old bodgy bearing.

Someone mentioned they had a generic part number for the Roller Bearing, I've come up with NF206, is this correct ?.
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Offline beezalex

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Re: Drive side crank bearing - Roller or Ball ?.
« Reply #4 on: 04.07. 2009 14:47 »
I've run two A65's with ball bearings and not had a problem.  One had it originally (a '62), the other I converted and rode hard on a daily basis for two years after.  I have since learned that setting up the endfloat on A10 and A65 cranks is a) not that hard and b) not that critical.  The same bike that I converted had previously run with .015" of thrust for a year of daily riding.

And Brian, my A50 is my most trouble-free bike.  It is my daily commuter now and I wouldn't trade it for the world.  Think of it as a long-stroke A7...
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Alex

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Offline trevinoz

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Re: Drive side crank bearing - Roller or Ball ?.
« Reply #5 on: 04.07. 2009 23:30 »
Josh,
       The main bearing is NF206 but it is a type that appears to be becoming hard to get. I once used a different one for a while, NJ I think, which had the rollers and outer race as one unit and the inner race only fitted to the crank. It seemed to work OK.
As to setting end float, I polish the crank journal until the bearing is a slide fit and set it. When all correct I fit the bearing with Loctite Bearing Mount. This has not created any problems, so far. I found it impossible to set the float without damaging the bearing if I left the shaft with the original fit.
Another way a Mate sets his is to fit the bearing to the crank and shim the outer race in the crankcase but I think that is too time consuming having to heat the case to remove the race each time if the shim is not right.
Trev.
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Online Brian

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Re: Drive side crank bearing - Roller or Ball ?.
« Reply #6 on: 05.07. 2009 00:16 »
Alex, dont know if this will help or not but when you go to your bearing company they may be able to cross reference one of these numbers.

The BSA part no. for the drive side roller bearing is   67-670

                                                                       Hoffman                R130L
                                                                       Skefko                  NFL30
                                                                       Ransome @ Marles  LRJA30
                                                                       Fischer                 NFL30

The A50 I had was a 1969 model and was a very nice bike, miles better than the A65. My last A65 was a 1970 Thunderbolt which I gave to my son. The A65's are a good design, if only they didnt vibrate so much.
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Offline Josh Cox

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Re: Drive side crank bearing - Roller or Ball ?.
« Reply #7 on: 05.07. 2009 15:28 »
Thanks Brian,

Have just removed a R130L.

Was around a guys place today who showed me a LJRA30, this is a fine bearing, hope I can find one, and post some photos.

Hoping not to enrage the engineering purists, if a roller bearing needs to be shimmed, why can't you shim it in the case house (drive side case), behind the bearing outer casing ? instead of on the crank behind the bearing inner case ?,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,I'll start running now.........
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Offline beezalex

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Re: Drive side crank bearing - Roller or Ball ?.
« Reply #8 on: 05.07. 2009 17:31 »
Hoping not to enrage the engineering purists, if a roller bearing needs to be shimmed, why can't you shim it in the case house (drive side case), behind the bearing outer casing ? instead of on the crank behind the bearing inner case ?,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,I'll start running now.........

There's nothing wrong with that except that the outer race is much harder to remove from the case than the inner is from the crank.  Otherwise, there's no real difference.
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Alex

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Offline olev

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Re: Drive side crank bearing - Roller or Ball ?.
« Reply #9 on: 06.07. 2009 11:50 »
How would a four point contact ball bearing work?
Something like a SKF QJ206MA.
http://www.skf.com/skf/productcatalogue/jsp/viewers/productTableViewer.jsp?presentationType=3&lang=en&tableName=1_3_4
The specs look good
cheers
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Offline Josh Cox

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Re: Drive side crank bearing - Roller or Ball ?.
« Reply #10 on: 06.07. 2009 12:01 »
The standard dimensions are (mm):
ID 30
OD 62
Width 16

So the QJ206MA would fit, wonder if they come in C3 ?.
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Offline Josh Cox

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Re: Drive side crank bearing - Roller or Ball ?.
« Reply #11 on: 20.07. 2009 05:58 »
Hello again,

Have looked at all options and am going with the ball journal, Bacon "twin", page 62 confirms for me that I am on the path I want to be. This bike is not engineered to space shuttle specifications and I will not be racing the bike.

Olev, the four point bearing looks good on paper, but the inner case is a two piece item, left and right, there would be no support on the drive side of the inner case.
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Offline trevinoz

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Re: Drive side crank bearing - Roller or Ball ?.
« Reply #12 on: 20.07. 2009 06:22 »
Josh,
 I feel that if the ball bearing was suitable, Bert Hopwood would have used it when he designed the engine.
The long stroke A7 was the basis of the later engines and it had a ball bearing but was dropped in the new series.
The first A65s used the same bearing as the long stroke but was changed to a roller and looking at an engine recently that some bright spark had substituted a ball for the roller, I can see why the roller should be used.
The ball was completely flogged out and in a condition that I have never in 40 years of playing with these engines seen in a roller.
Why do you want to change? The roller, if properly shimmed on assembly, will not give you any trouble.
  Trev.
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