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BSA Drive Side Bearing #733387
04/28/18 2:23 pm
04/28/18 2:23 pm
Joined: Dec 2010
Posts: 37
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amx-bsa Offline OP
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I'm currently rebuilding the motor on a '67 hornet. This is my second BSA rebuild (first was a ‘65 T bolt).
The Drive side roller bearing seems OK, however I was considering replacing it with a new Bearing while I have the cases apart.
Before I do, I have a couple of questions:
• Can I use a ball Ball bearing set up like the 65 motor I previously built?
• I understand that the ball will not be as strong as the roller, but it shouldn't be any weaker than the set up used in earlier model A65, right? Or am I missing something?
• The earlier motor didn't include a thrust washer on the timing side, will is still need it if I use a ball bearing?
• my current Timing side bush measures out fine, and I wasn't going to replace it? Will I need to if I install a New Ball Bearing in the Drive side?

I suspect this maybe more complicated than just swapping out bearings, So I'd really like to get this right.

I appreciate all the help and advice I can get from anybody that's done this before.


'67 Bsa Hornet Rolling Basket case
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Re: BSA Drive Side Bearing [Re: amx-bsa] #733399
04/28/18 3:57 pm
04/28/18 3:57 pm
Joined: Dec 2004
Posts: 9,293
Scotland
kommando Offline
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Quote
I understand that the ball will not be as strong as the roller

Correct

Quote
but it shouldn't be any weaker than the set up used in earlier model A65, right?

Correct

Quote
Or am I missing something?


No

Quote
The earlier motor didn't include a thrust washer on the timing side, will is still need it if I use a ball bearing?


The ball bearing controls the endfloat so the thrushwasher is not strictly needed but you still need to ensure the crank with the new bearing is in the middle of the cases so the rods are in the middle of the bores and this may need shims and a way to protect them plus the cases dimensions did change so it may be best to install the thrust washer.

Quote
My current Timing side bush measures out fine, and I wasn't going to replace it?

1.5 thou clearance ?

Quote
Will I need to if I install a New Ball Bearing in the Drive side?


No, rolling element bearings are precision made well enough there is no need for a new timing bush if it checks out.

Re: BSA Drive Side Bearing [Re: kommando] #733415
04/28/18 8:01 pm
04/28/18 8:01 pm
Joined: Dec 2010
Posts: 37
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amx-bsa Offline OP
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Thanks for the info.

My timing side bush measures in spec.... my thrust washer seems thin at around .043 thousands . I’m not sure what the specs are. The older timing side bushes seem to be different between years, it’s good to hear that it won’t matter


'67 Bsa Hornet Rolling Basket case
Re: BSA Drive Side Bearing [Re: amx-bsa] #733445
04/29/18 4:47 am
04/29/18 4:47 am
Joined: Dec 2002
Posts: 3,246
arkansas
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leon bee Offline
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arkansas
I'm not one of the rocket surgeons here, but I've done this 3 times- no problems at all. Look for a good bearing, I think the last one I did was a FAG brand bearing.

Re: BSA Drive Side Bearing [Re: leon bee] #733544
04/30/18 1:26 am
04/30/18 1:26 am
Joined: Aug 2001
Posts: 137
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Phil R Offline
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AMX

Mr Mike did a fairly comprehensive write-up on this board regarding his use of a ball bearing in place of the roller bearing on the drive side of an A65.
The post was dated: 11/1/2010 and was in response to an original post by "Twairds" : Setting A65 Crank End Float.
It's worth the read if you do a search to find it. He used a Japanese bearing type RMS-9, manufactured by JAF.
The switch to the ball type worked well for him.
HTH
Phil

Re: BSA Drive Side Bearing [Re: amx-bsa] #733567
04/30/18 11:39 am
04/30/18 11:39 am
Joined: May 2013
Posts: 4,828
Rotherham - S. Yorkshire
Allan Gill Offline

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I use the ball on my setup and do prefer it.

I would set the endfloat with the thrust washer in place, however if you chose to remove it then that is up to you on final assembly.


beerchug
Re: BSA Drive Side Bearing [Re: amx-bsa] #733572
04/30/18 12:02 pm
04/30/18 12:02 pm
Joined: Aug 2001
Posts: 5,033
Stone Creek OH USA
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Rich B Offline

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You need to set the "end float" with the thrust washer in place to correctly position the crank. Reality is, it isn't end float but "running clearance" for the crank with the ball bearing. But you need the thrust washer in place to do it correctly. Use .0015" - .003" like the roller bearing motor.

Most modern ball bearings use a larger inner race than the original 62 - 65 style bearing. So you should be good to go with larger shim cup from the roller bearing engine.

Make sure you shim primary chain alignment after the bottom end is complete to keep from thrust loading the ball bearing.

With modern oils and the way the bikes get used today, IMO, this is a decent conversion. I run both ball and roller bearings in A65's. If I didn't have a new roller bearing looking for a home, the next A65 (also a 66 Hornet) would get the ball conversion.


Life is too short to drink cheap, bad beer.
Re: BSA Drive Side Bearing [Re: amx-bsa] #733586
04/30/18 3:24 pm
04/30/18 3:24 pm
Joined: Jan 2004
Posts: 3,672
ca, us
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DMadigan Offline
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The ball bearing sets the end float. The case has a lip to keep the bearing from moving out the drive side but nothing on the crank side of the bearing. The thrust washer keeps the crank and bearing from walking out of the case toward the timing side.Loctite bearing mount can be used to keep the bearing in place but the thrust washer is insurance.
Clarification:
Thrust washer - the bronze faced washer on timing side used on later engines with roller drive side bearing.
Shims - between the drive bearing and crank to position the crank in the case, held in a cup

Re: BSA Drive Side Bearing [Re: amx-bsa] #733591
04/30/18 4:39 pm
04/30/18 4:39 pm
Joined: Nov 2012
Posts: 576
Isle of Wight, UK
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koan58 Offline
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If the crank is located by a clamped up ball bearing on the drive side, what purpose is a thrust washer on the timing side doing?

Use of a triplex primary chain requires primary sprocket alignment precision. Whichever arrangement you choose, you will need to accurately set this with shims/thrust washers.

As Kom said, the centrality of the rods in the bores is also worth checking.

The thrust washer/roller bearing set up does allow a limited end float of the crank, in turn allowing a certain degree of primary self-alignment (by axial movement of the crank), which IMHO would be better for both main bearing and primary chain (provided the perfect primary alignment is within the limits of crank float).

If there is significant primary mis-alignment (others will have more experience but I'd hazard a guess at 10 thou max) then the ball bearing will suffer from continuous excessive axial loading, or in the case of a roller, it will either fail where the rollers grind against the lip, or the thrust washer will be subject to continuous load.

Re: BSA Drive Side Bearing [Re: koan58] #733612
04/30/18 7:05 pm
04/30/18 7:05 pm
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Stone Creek OH USA
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Rich B Offline

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"If the crank is located by a clamped up ball bearing on the drive side, what purpose is a thrust washer on the timing side doing?"

Not much, other than allow you to properly locate the crank in the cases when setting "end float" (running clearance) of the crank.


Life is too short to drink cheap, bad beer.
Re: BSA Drive Side Bearing [Re: amx-bsa] #733614
04/30/18 7:18 pm
04/30/18 7:18 pm
Joined: Dec 2004
Posts: 9,293
Scotland
kommando Offline
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Loctite bearing mount on a steel bearing in an alloy case has the potential to give 2 issues, the Loctite can change the stress on the bearing and decrease the internal clearances, and the Loctite gives up too soon possibly caused by too much differential expansion between the steel and alloy. Tried it twice on the same engine and it lasted 1000 miles each time, never did it again, if the bearing interference fit in the alloy housing is too much, fix the fit.

Re: BSA Drive Side Bearing [Re: Rich B] #733622
04/30/18 8:28 pm
04/30/18 8:28 pm
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Isle of Wight, UK
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koan58 Offline
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If using a roller bearing, the axial freedom of the crank must be limited to a small number of thou by the thrust washer and shims (if necessary).

The thickness of the thrust washer and where and what shims are used will determine whether the rods sit centrally in the bores. (this assumes everything is good, square and straight).

If using a ball bearing, which then clamps up and dictates crank position, you should first set rods centrality using shims between bearing and crank cheek, then you will know the gap on the timing side for a washer, if you feel the need for one.

Either way, I'd recommend checking primary alignment afterwards.

Re: BSA Drive Side Bearing [Re: koan58] #733642
04/30/18 11:24 pm
04/30/18 11:24 pm
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Posts: 37
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amx-bsa Offline OP
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Thanks for all the help and info.

Are there different sizes of thrust washers in order to locate the rods in the correct orientation to the cylinder bores ?

Thanks
Tony


'67 Bsa Hornet Rolling Basket case
Re: BSA Drive Side Bearing [Re: amx-bsa] #733652
05/01/18 12:23 am
05/01/18 12:23 am
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DMadigan Offline
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"Are there different sizes of thrust washers in order to locate the rods in the correct orientation to the cylinder bores ?"
No (I have not heard of different thickness thrust washers 68-0685), but there are different thickness shims that go between the crank web and bearing to centre the crank.

Re: BSA Drive Side Bearing [Re: amx-bsa] #733664
05/01/18 3:04 am
05/01/18 3:04 am
Joined: Aug 2001
Posts: 4,404
Owego, NY, USA
Mark Z Online content
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Mark Z  Online Content
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Originally Posted by amx-bsa
Thanks for all the help and info.

Are there different sizes of thrust washers in order to locate the rods in the correct orientation to the cylinder bores ?

Thanks
Tony


Since the crank is clamped to the drive side bearing by the rotor nut, the positioning of the rod journals is determined by the drive side. The rod journals are wider than the rods, so there is some built-in tolerance there.

I don't know if you can get the crank to move axially with the ball bearing in place, so if you haven't yet removed the roller bearing, check end-play on the crank with the roller bearing, and make sure there is adequate running clearance in the case (1.5 to 2 thou). Then measure the thickness of the ball bearing vs. the thickness of the roller bearing. If they are the same, then your crank setup will be the same. Otherwise, adjust your shims accordingly.


Mark Z

'65(lower)/'66(upper, wheels, front end, controls)/'67(seat, exhaust, fuel tank, headlamp)/'70(frame) A65 Bitsa.
Re: BSA Drive Side Bearing [Re: amx-bsa] #733694
05/01/18 9:30 am
05/01/18 9:30 am
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Posts: 5,033
Stone Creek OH USA
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Rich B Offline

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Every time someone asks about a BSA bottom end, posts show up going on and on about centering the rods in the bores. Unless BSA really screwed up with the design and machining......that work is already completed for you.

Unless you just plain leave some significant parts completely out of the bottom end, the crank journals are going to be where they need to be. You can only shift the crank by a very tiny amount with the shims on the drive side.

Put the pieces back in the bottom end as specified by the parts book for the year you are building. Set the crank end float (.0015 - .003”) per the service manual, and the crank is properly located. It isn’t rocket science.

Note - with a ball bearing, you set end float with the DS end of the crank unloaded. You are setting running clearance of the crank in the cases. When the engine is fully assembled, the crank is locked in position.

With a roller bearing crank, you load the DS of the crank to set end float, you really are setting float. When the engine is fully assembled, the crank does move slightly in the cases.


Life is too short to drink cheap, bad beer.
Re: BSA Drive Side Bearing [Re: Rich B] #733758
05/02/18 1:57 am
05/02/18 1:57 am
Joined: Aug 2001
Posts: 4,404
Owego, NY, USA
Mark Z Online content
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Originally Posted by Rich B
Note - with a ball bearing, you set end float with the DS end of the crank unloaded.


Rich, I was hoping you'd chime in, and I'm relieved to see I was on the money about most of it, except for missing the above. Of course, with the rotor nut not tightened down, the crank will be able to move enough to check/set end float.


Mark Z

'65(lower)/'66(upper, wheels, front end, controls)/'67(seat, exhaust, fuel tank, headlamp)/'70(frame) A65 Bitsa.
Re: BSA Drive Side Bearing [Re: Mark Z] #734356
05/07/18 4:33 am
05/07/18 4:33 am
Joined: Dec 2010
Posts: 37
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amx-bsa Offline OP
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Update: I desided to use a ball bearing instead of the roller.....
I'm reinstalling the thrust washer because.... I have one....
I'll check the rod positioning in the bore.... but I don't expected any changes, because the crank and cases are original.... not something cobbled together from bits.....
I hope to have the bottom end finished this weekend.

Thanks once again for all the help and advice

Tony


'67 Bsa Hornet Rolling Basket case

Moderated by  Allan Gill, Jon W. Whitley 


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