The BSA A7-A10 Forum

Technical => A7 & A10 Engine => Topic started by: huddie on 17.09. 2012 11:25

Title: Crank end float
Post by: huddie on 17.09. 2012 11:25
Hi All, Following on from my topic on Thrust washer debris I am about to rebuild it and was wondering what is the best way to measure crank end float. As one is dealing with a fairly weighty piece of metal where and how does one measure in order to get it right.
Regards Huddie
Title: Re: Crank end float
Post by: bsa-bill on 17.09. 2012 15:56
A dial gauge is a good buy and not too expensive these days.
Also as has been said on here recently use the old bearing, put the crank in the cases and bolt it up tight ( don't need to use all the studs though ) measure the end float several times until your happy you have a good reading.
Then strip it down take off the old bearing and measure it, then measure the new bearing note any difference and add or take it away from the end float you had established next take 1.5 thou off the said end float and the result will  be the amount of shimming you need to put on the crank before slipping on the bearing.

a case of measure many times and do the job once.
If you have no dial gauge then vernier callipers will do but take many more measurings until your happy, Ive done it twice once with callipers and once with a dial gauige, got pretty good results eventually but it takes patience and time
Title: Re: Crank end float
Post by: huddie on 17.09. 2012 18:37
Cheers Bill, wouldn't of thought of using the old bearing. This way means the new one only being fitted once.
Thanks for that.
Regards Chris
Title: Re: Crank end float
Post by: duTch on 18.09. 2012 10:45

 I put the bearing inner in place with cases together, used a bit of threaded rod (booker rod?) with a menagerie of  locknuts and washers done up 'tight' against the bearings, then measured the overall, and subtracted the crank width.
 Am yet to see if the results work ok ,
Title: Re: Crank end float
Post by: KiwiGF on 18.09. 2012 11:48
If you have a means of spinning the old bearing inner eg a lathe it does not take much to make it a loose fit on the crankshaft using emery cloth on the bearing inner. This means you can refit the old bearing as many times as you like easily and adjust the shims, all without damaging/wearing the crank.

If the old and new bearings are a different thickness (eg measured from outer face of outer race to inner face if inner race)  due to wear etc this needs to be measured and taken into account but does not prevent you using the "old bearing" method.

Does that make sense? I hope so!
Title: Re: Crank end float
Post by: Greybeard on 30.09. 2012 18:45
I've just been setting my crank endfloat. I bolted a piece of steel across the timing case and attached my magnetic dial guage to it. This link should take you to a picture of the operation. (http://)

Neil Ives
Title: Re: Crank end float
Post by: Greybeard on 30.09. 2012 18:50

Try this link.

Title: Re: Crank end float
Post by: huddie on 21.12. 2012 15:34
Hi All, Merry Christmas to you all. Long time since I commented on this topic, thats because my crank and relevant bits have been away for dynamic balancing, hopefully to get rid of some of the vibration.
Just put the crankcases back together to check the end float and need a bit of advice.
I have taken the reading several times (properly this time using a solidly mounted dial gauge), and using the old bearing. I was a bit suprised that the end float is showing 0.030mm which is roughly 0.0012". Almost seems like it doesn't need any shims.
Is this usual, and what are the min and max values for end float. Nothing sensible in my Haynes comic.
Obviously I will have to measure the old bearing against the new one and adjust, but if the new one was any thicker than the old one then my endfloat would have all but disappeared, is this ok!
Regards Huddie
Title: Re: Crank end float
Post by: bsa-bill on 21.12. 2012 17:10
Hi Huddie
Did you have the timing side bush replaced ? I can't recall.
If so it could be the new bush has a bit thicker face - just make sure it is seated right down into the case, careful here use heat on the case and pull the bush in rather that the tempting "give it a tap" method.
Don't know much about the balancing procedure, do they split the crank shouldn't think they need to but others might like to comment here, just wonder if the crank could "grow" in those circumstances.

I'm only a two As guy so can't say what the norm is but my last one had very little clearance, it did need a shim and ended up just on 1 thou so quite possible all is ok, no reason to think BSA couldn't work to close tolerance even all those years ago, if once bolted up it spins free with the old bearing and the new one is no more than 7 thou more I'd be happy, once again there are members who've done this more times than I and no doubt will give more info

OOPS 7 thou more, should have been a decimal point and a couple of zeros in there
Title: Re: Crank end float
Post by: duTch on 22.12. 2012 13:42
Hiya Huddie, I've been led to believe that's close to ideal, so long as 'all of the above' applies- you might've got lucky!!
Title: Re: Crank end float
Post by: huddie on 04.01. 2013 18:55
Happy new year everybody, Here's where I am with this end float. There was some float, good job I checked again. The dial gauge was moving on the stand bar!!. The thread on the clamp was gone, new dial gauge stand and all, so a delay while this went back to the man'f for replacement. Thought I had it measured right with the old bearing but alas with the new one in plus shims there is still to much float. Now my question is that aiming for about 1.5 thou I am assuming I will need to use a small lever between the crank web and the crankcase or should I be able to move the crank by hand. Also I have been checking the clearance with both the drive side bearing and the timing bush running dry. Should this be done dry or lubed?
Appreciate your help guys because I would like to make sure this is spot on this time.
Regards Huddie
Title: Re: Crank end float
Post by: muskrat on 04.01. 2013 19:54
 G'day huddie. All clearances are measured dry. When checking crank end float I do all the crank case nuts/bolts up finger tight, give the cases and crank a few light taps with a hide mallet and turn crank a few times. Give all the nuts/bolts another 1/8 turn and do it all again. Done in a few stages till all done up to about 15ft/lb. The crank should be free to move by hand but a lever can be used as you mention or a light tap with the mallet on the shaft ends just to make sure.
Title: Re: Crank end float
Post by: bsa-bill on 04.01. 2013 21:17
My last project went drum tight when the studs were turned up leading me to think there was no float, after much faffing about for far too long I discovered there was float and a lot  of it but needed a lever to shift the crank.
Took it back to the shop that line bored it, they got it right second time but wouldn't say what was wrong (obviously I suspect it was not bored true).
Anyway a gentle pry with a bar will confirm the float
Title: Re: Crank end float
Post by: Slide on 05.01. 2013 21:32
I used a small strip of metal (see attachment) bolted to one of the oil pump mounting holes. Then I used a set of accurate feeler gauges to measure the end float. Simple, but I found it quite effective and was able to work out the shim thickness quite easily.

For info I've also enclosed a pic of the bearing extractor gizzmo I put together to remove the bearing, rather heavy-duty based on a Clarke bearing puller from 'Machine Mart' in the UK, but it did the job..

Title: Re: Crank end float
Post by: muskrat on 05.01. 2013 23:45
 G'day Mark, that's almost a dead ringer of my puller.
We seem to go to great lengths and delicacy to put them together. But, like jam, if you saw how it was done in the factory you wouldn't eat it. *eek*
Title: Re: Crank end float
Post by: Slide on 06.01. 2013 17:32
Hi Muskrat, thanks for the comment. Good to hear I have come up with something similar to someone as experienced as yourself. I have used the Forum quite a lot to help with my rebuilding of an A7SS - my first experience wth BSAs *smile*. Having just finished the project I thought it was about time I actually joined the Forum - looking forward to giving back some of my lessons learned and picking up a few more tips too..
If you'd like a quick story (a bit off topic) - I have a family history dating right back to the mid 1800s in BSA. My surname is Aston, a well known name in Birmingham where BSA were based. My uncle tells me my great grandfather was one of the original founders of BSA (a gunsmith). So I thought I should get hold of a BSA machine to tinker with (about time as I'm in my 50s now)! All the best for now..

Title: Re: Crank end float
Post by: olev on 07.01. 2013 12:01
This thread rings a bell.
Didn't you build a motor using a ball bearing main with no float?
I was interested in this as it always seemed to me to be the proper way to design an engine.
How did it behave?
hope the new year is treating you well.
Title: Re: Crank end float
Post by: Brian on 07.01. 2013 12:16
Yes, the plunger A10 bitsa I built I used a ball bearing. I've only done about 2,000 miles on that particular bike so far, when it gets to about 40,000 I'll know for sure !

I did it as a "see what happens" experiment. The ball doesnt have the radial load ability of a roller but I believe in a low stressed motor it will be adequate. That motor is running 7.25-1 with a 356 cam.

When BSA introduced the A65 for the first few years they went back to a ball bearing. Late BSA Bill (RIP) used ball bearings in his motors and swore by them.

The big advantage of course is you dont have any end float to worry about, when the cush drive is done up the crank is held in place by the bearing.
Title: Re: Crank end float
Post by: huddie on 21.01. 2013 15:09
Hi to you all, Here's the latest on my endfloat prob. Thought I'd got it right but when I did what I thought was the final assembly not only have I got no end float but as I tighten the cases the crank tightens up to the point where it is difficult to turn.
I haven't repaced the timing side bush or the drive side bearing, both being in good nick as the bike had only done about 200 miles since a rebuild before the thin endfloat shim broke up.
Am I correct that if the shimming is wrong ie to many then it could cause the symptoms of the crank going tight?The crank spins fine with the cases together, tapped with a mallet and the nuts done up finger tight. but as soon as I apply any tension to the nuts (done a little at a time and in sequence) the crank needs effort to turn and then a little more tension and it tightens up. The tension applied is only a little past finger tight nowhere near what I had it done up to when checking the float.
Now also as I am about to take it apart again and go back to square one I want to get the bearing inner off the crank without damaging it. It has been built with a bit of bearing tight on the inner so it might not come off to easily. I have access to a puller like the one in "Slides" reply but my worry is getting the jaws far enough under the bearing so that it pulls against the inner not the roller cage. How does one do that?.
Regards Huddie
Title: Re: Crank end float
Post by: Goldy on 21.01. 2013 16:01
Hi huddie. If the crankcase bolts where tight when you did the end float, and you obtained the three thou float then simply assembling would not change anything, so I would look for something else. You ask about removing the bearing, I use a small chisel which I ground down to a very shallow angle. Tap the chisel in behind the bearing a little bit at a time each side until the bearing moves enough to be able to get a small puller behind it.
All the best Goldy
Title: Re: Crank end float
Post by: bsa-bill on 21.01. 2013 18:37
not only have I got no end float but as I tighten the cases the crank tightens up to the point where it is difficult to turn.

this is exactly the same problem I encountered, unfortunately I can't give an explanation as the shop I took it to (with another new timing side bush) said they had done exactly the same as they did the first time but this time it was perfect (well they would say that wouldn't they).
My suspicion based on little experience or skill is that the first line bore they did was off line or off centre and the final tighten just nipped the crank up, not very scientific I know but the best I can guess, someone here with more know how re line boring might like to comment, but I think it might be a plan to take it back to whoever did it for there opinion
Title: Re: Crank end float
Post by: huddie on 21.01. 2013 20:59
Hi Bill, Mine hasn't had the bush or the bearing changed. It was stripped because of the broken shim. It was all running fine before so it should be alright now! but it isnt. Back to the question in my last post, will it tighten up if there are two many shims??
Regards Huddie
Title: Re: Crank end float
Post by: chaterlea25 on 21.01. 2013 21:19
Hi Huddie,
"Back to the question in my last post, will it tighten up if there are two many shims??"

Yes it will  *sad2*
To shim it correctly all the crankcase bolts need to be fully tightened, before measuring end float
Check the both case halves are level at the crankcase mouth
sometimes the cases need a little tap to align properly

Title: Re: Crank end float
Post by: Goldy on 21.01. 2013 22:23
Huddie. just a thought but whilst its been dismantled have the crankcase alignment dowels got damaged or missing.
Title: Re: Crank end float
Post by: huddie on 22.01. 2013 08:38
Thanks Chaterlea and Goldy, its got to come apart so I will check the dowels and go through the shimming exercise again. Anyone any idea what the torque should be on the crankcase bolts?.
Regards Huddie
Title: Re: Crank end float
Post by: Billybream on 22.01. 2013 10:12
Hi Huddie.
Been following your thread with interest, you will struggle to find any official torque settings for the crankcase half bolts/nuts, I have used typical settings off A65 as a guide for same thread size (already suggested on another thread) , secret is to keep them the same value. The other really useful tip is to use a dummy bearing to set end float.

Torque wrench settings (Dry)
BSA A50 & A65 Unit Twins                1962-65    1966-68    1969-70
Flywheel bolts                                 30lb/ft    30lb/ft    45lb/ft
Connecting rod nuts                         22lb/ft    22lb/ft    22lb/ft
Cylinder head bolts 3/8"                    25lb/ft    25lb/ft    28-30lb/ft
Cylinder head bolts 5/16"                   25lb/ft    25lb/ft     
Cylinder head nuts 3/8"                     26lb/ft    26lb/ft    31-33lb/ft
Cylinder barrel nuts 5/16"                  18lb/ft    18lb/ft    18-20lb/ft
Oil pump stud nuts                            7lb/ft    7lb/ft    8-10lb/ft
Clutch centre nut                       70-75lb/ft    70-75lb/ft    65-70lb/ft
Kickstarter ratchet nut                      60lb/ft    60lb/ft    55-60lb/ft
Rotor fixing nut                                60lb/ft    60lb/ft    60lb/ft
Stator fixing nuts                          10-15lb/ft    10-15lb/ft    5-7lb/ft
Crankshaft pinion nut                       60lb/ft    16-18lb/ft
Carburettor flange nuts                    10lb/ft   10lb/ft    10lb/ft
Manifold stud nut 5/16"                    12,5lb/ft    12,5lb/ft     
Manifold stud nuts 1/4"                    6lb/ft    6lb/ft    6lb/ft
Zener diod fixing nut                        17lb/ft     
Title: Re: Crank end float
Post by: Slide on 23.01. 2013 20:20
when I used the bearing puller (see picture above) I very gradually squeezed the jaws closed and re-positioned the puller as necessary as the bearing started to pull away. I found pullers to be so much more effective than for example using a fine chisel to start it off. A puller keeps the force really square which is essential. I was probably pulling on the outer shell to start with to get it moving, can't quite remember..
good luck with it
Title: Re: Crank end float
Post by: huddie on 24.01. 2013 15:14
Hi All, Thanks for the info Slide, Softly softly seems to be the way with the puller, it was definitely pulling on the roller cage to start but it came of eventually, not so sure using bearing tight is such a good idea. Thanks for the torque info Billybream, the case nuts were not on there but the rest will come in handy. So I got it all apart and started from scratch again, guess what it all went back together again and this time its fine. Finished up with 1.67 thou endfloat wich looks fine. I did use a new bearing and as for what was wrong before, I can only guess, but I think it may have been that the bearing outer did not go into the crankcase square. I didn't have an appropriate size sleeve for the press and had used three sockets one on top of the other to get a deep enough sleeve to clear the crankcase studs which were still in the l/h side.
So today before fitting the new bearing outer I bought a suitable sleeve, 39mm deep socket did the trick, very cheap compared to a bearing sleeve kit.
I have done the case nuts up to 20 ft/lbs, any comments any one?
Just the remainder of the rebuild to do now, roll on Spring.
Regards Huddie
Title: Re: Crank end float
Post by: trevinoz on 24.01. 2013 20:13
                   If you heat the crankcase, as you should, the bearing outer will drop in.

Title: Re: Crank end float
Post by: a10gf on 26.01. 2013 23:00
Slide, am appreciating the endfloat measurement (,6119.msg45320.html#msg45320) process and picture.
Title: Re: Crank end float
Post by: Slide on 10.02. 2013 21:52
a10gf - glad you liked the endfloat picture/process. Was simple and quick, after I got in a mess with various other tricky methods..