Crankcase bearings

[Oval57]

Llittle confused,
can someone confirm the correct installation of the crankcase bearings on a 1930 500 sloper please?
Parts book lists
Engine Shaft Drive side........... Roller Bearing
Engine Shaft Gearside......... Roller Bearing
Crankcase Main Shaft ..........Ball Bearing
What is deemed the crankcase mainshaft ?
Then to confuse things the Useful data which appears to be the closest thing to a workshop manual lists bearing requirements as
1 X Roller Bearing
2 x Ball type
Which is different to above and again what location
My engine i have stripped has three ball type fitted ?

Next question
Does any one have outside and bore dimensions of the .005 / .010 spacer shims referred to whilst setting up endfloat on the crank
Thanks
Roger

[Steve.S]

At the begining of the '30's BSA changed the bearing arrangement a few times.
For the last 30,000 miles, I have been using 2 roller bearings and 1 ball bearing. The ball bearing is fitted first, followed by the spacer ring and then the roller bearing. The other roller bearing is fitted to the other side. The roller bearing I used was an NSK NF305.
The bearings are 25mm bore, 62mm OD, 17mm wide.
However, the 'Motorcycling' article dated may 19th 1955 states 2 ball bearings and 1 roller bearing. If you search the Forum you should find it.
Then there is an article in 'The Motor Cycle' magazine dated September 1932 quoting a ball and roller on the drive side and a roller on the timing side, and this is the arrangement I have used, so it's up to you.
The crankshaft Main Shaft referred  to will be the drive side engine shaft.
Having 3 ball bearings will probably be OK, but a roller bearing is better able to take the drive thrust.
The bore of the shims will be 25mm to fit the mainshaft and the OD will be the OD of the inner race of the bearing. 

[militaryron]

Just to double up what Steve is saying. By the 40's for the M20, BSA had also decided that you can use two roller bearings on the drive side or alternatively one roller and one ball bearing...The ball bearing being the outer one. Ron

[JulianS]

I think this 1930 service sheet may give the bore of the shims?

[Oval57]

Thanks to all that replied, going to run with One ball and two rollers....

[Oval57]

I fitted my Bearing on the weekend in the following configuration.
Ball Bearing, Spacer, Roller bearing with a roller bearing fitted to the other side.... everything turns freely and feels great!
However I may be missing something here, I noticed that on the drive side with the Ball and Roller, what keeps the roller part of the bearing from moving outwards towards the ball bearing? the spacer keeps the outers apart, but the inner can slide along the crank, I may be overthinking but wouldn't the fact that the inner roller bearing can move you can't really check for end float

[chapmast]

There should also be an inner spacer that is the same length as the outer spacer. Although there should be a lip on the outer shell of the roller bearing that also stops the inner from moving, the inner spacer is really meant to fulfil this job.

The end float is dealt with by the ball race - it's a thrust bearing that is there to prevent the crankshaft from drifting in the axial direction.

[Steve.S]

It might be worth bearing (no pun intended) in mind that there are differences between the 1929 engines and the 1930/31 engines.
BSA did not fit the inner spacing collar 24-725 to the 30/31 engines, only the '29 and earlier models. Perhaps because of the possibility of it pre-loading the roller bearing. Who knows?
This inner spacer is not mentioned in the 1930 Parts Book.
BSA also deleted the 2 Ballrace Pegs EA 94 in 1930.
I believe the flange on the inner roller bearing race should be fitted towards the ball bearing.
I hope this helps.
It seems odd that you are not using the correct piston. Thorntons still stock many pistons, and the Sloper piston is currently in stock.
However, it's your motorcycle, and of course, you can fit any piston you like. (Same with valves.)

[Oval57]

Thanks for the info Steve.S
"BSA did not fit the inner spacing collar 24-725 to the 30/31 engines, only the '29 and earlier models"
OK .... now it gets confusing.... I also notice on the 29 there was two ball bearings and one Roller with the ball bearings being separated by an inner and an outer spacer
Then ... they decide to go to a Ball and a roller bearing on one side only separated by an outer spacer ....
So ... what stops the inner from sliding back and forth almost out of its outer race if it goes towards the ball bearing??? And how do you check and set end float if nothing is locking the shaft in position???
going to machine myself up an inner collar and keep facing it until i get my endfloat correct
mmmmm interesting to say the least

Reason for the piston change is to get the third ring, I seen some originals in England freight is the killer unless I had a big shopping list to make it worthwhile
Valves ... I would love to use standard but couldn't seem to find any anywhere ...
Cheers

[chapmast]

I'm really surprised that BSA did not continue to fit the inner spacer. The bearing arrangement on the post war B and M series is essentially the same and all use an inner spacer. The outer lip of the bearing isn't really designed to take axial loading as it will press directly onto the outer edge of the rollers. An inner spacer will press on the solid metal work of the bearing. I would definitely make an inner spacer, especially when later post war models had this arrangement - when BSA finally got things right.

I think BSA kept changing their minds in this area. My 1928 Sloper had 3 ball races fitted - they were all pre war items so I'm unsure if they were fitted by the factory or a later owner. I chose to use 2 rollers and a ball race because this is the same arrangement as the B/M series machines.

The FW Thornton pistons are Side Valve items ( JP 01084) with a compression height of 42mm which is far too tall and cannot be modified. I think Mark Quinney bought the last OHV piston from them.

On a slightly different topic the timing side bush will probably be worn and a felt or leather washer is used to help keep the oil in. Mark Quinney showed me a modification what had been made to his bike where an oil seal had  been fitted to the bush. I made the same modification to my bike, but added a circlip to retain the oil seal - I've added some pictures.

The second picture shows an original bearing in the middle - note the groove and small channel that feeds into it. This supplies oil to the cams. The timing side nut has had to be machined so that it can clear the circlip - I also had to file a small amount of metal off the circlip itself. The best way of removing the original bearing is to slowly drill it out by going up in drill sizes 1/64 at a time. When the wall of the bearing becomes very narrow it will collapse and be pulled out by the drill. When fitting the new bearing do not overheat the alloy cover as its an odd shape and you could crack it.

[Steve.S]

Mr. Oval, Your first 3 sentences are correct. Since you know what year's your engines are, you now know the BSA bearing set up the factory used (for whatever reason.)
Well now, would you believe I've just located the roller bearing I replaced 30 years ago. The outer race has a lip on the outside (when fitted), and since this outer is held solidly in the crankcase and cannot move, and the inner race is double lipped, then the inner race cannot move outwards because rollers will tend to bear against the lip on the outer race preventing the inner race from moving towards the ball bearing. Now it must be that there is not much thrust acting here, because roller bearings are not designed to bear much side thrust.
The bearing I use is an NSK NF 305, an Oriental product I believe. I wonder if you have the correct bearing?
All I can tell you is that I have been using the setup I previously described, without the inner spacing collar (as BSA intended for 1930 to the end of Sloper production) for the last 30,000 hard miles, (after all, these things were built to be thrashed), with not the slightest problem. However, who knows what will happen tomorrow?
So, there you have it, but the choice is entirely yours. You must do what you think best.
I very much take on board what Mr. Chapmast has said about later engines, but as I said before, my concern would be the possibility of the inner collar creating axial thrust and premature wear of the roller bearing, unless you were extremely accurate with the thickness of the collar. But what do I know?
Now, regarding endfloat, I take it you have read Service Sheet No.15? (And also No.15.)
I don't quite understand when you say "nothing is locking the shaft in position."
To check the endfloat, you would simply assemble the crankcases and grasp the mainshaft and try to move it back and forth. You could use a DTI to measure it. (The crankshaft would move in and out of all the inner races, as it did when you fitted the crankshaft, if you see what I mean.) BSA say endfloat should be nil, but the flywheel assy should be perfectly free to rotate. If it's too tight, BSA recommend assembling the crankcases with a sealant (which I think we all do anyhow.) But you may prefer to shave a little off the flywheel cheek?
If there's too much endfloat just fit shim(s) between the flywheel cheek and the roller bearing. But do check the con rod is central.
I remember reading a SKFCO article that suggested all ball bearings should run with a tiny amount of preload, but whether you can be bothered with this is up to you.
I'm going to have a lie down now, but do let us know if this hasn't answered your questions, and I'll have another bash.

[Steve.S]

Regarding pistons, the Hepolite number for the 493cc OHV Sloper is 2687.
I happened to be speaking to Thorntons a few days ago, so asked them if they had this piston in stock and they told me that they had this piston in stock under the Hepolite Part Number, in 3 different sizes.
The fellow even unboxed one to confirm that it had an oil control ring at the top, which it did.
Perhaps they've restocked since Mark bought his?
Mr. Chapmast, your modification looks magnificent. I think you should go into series production.
Not having your engineering skills or equipment, I'm ashamed to say that not having the correct hard felt conical seal, I used 2 felt Corn Pads. Seems to have worked quite well for the last 30 years, without any apparent problems. But as I said before, who knows what will happen tomorrow?

[Oval57]

I appear to have thrown the proverbial cat amongst the pigeons here!!!!!!
Thank you both for your responses..

I am probably at the stage where I have two choices, either jump on the lathe and knock up a spacer or reheat the case remove and replace the two bearings with Ball type ... I think I need to sit and ponder on this one
 
Steve.S the bearing I used was a NSK N305W ... obviously being unaware of the problem that has arisen my local ball bearing man supplied this based on the sizes I supplied and the application that I described to him also showing him the cutaway picture that is in the handbook .. never mind only a minor hiccup

Endfloat well, I still can't get my head around it.... I've rebuilt many a A65 engine and they have a Thrust face to pull up against, to me the crank on the sloper can float around, I need to stop and have another good read of what literature there is around and maybe I'm over thinking it as I tend to do ... need to sit and ponder a bit on this one too

Thorntons.. I reckon when I checked their website along with many others when I first started hunting a piston they only showed the side valve one then, so I moved on to alternative ... I spoke with one of our BSA club members and he had fitted the piston I am getting to his engine, and it is very successful, so I suppose I will give it a go, but again thanks for following it up

Timing cover Bush.. I machined a new one of these up as mine was worn , to remove the old one I warmed the case and used a large tap , as it screws in it bottoms out and winds the old bush out , if it doesn't move you need to be a bit warmer, surprising how little amount of heat is required, slip the new bush in and away you go .... thought a seal would be a better option but decided to head with the felt seal as per std.(Chemist has run out of corn pads ) not knowing what clearances I would have. the groove and channel in the bush need to line up with an oil feed hole in the casing. (overthinking again) But? your circlip where is that located? does it just go behind the seal on the crank, no locating groove??

Well, I reckon I've caused enough havoc this morning time for a brew

[Oval57]

I appear to have thrown the proverbial cat amongst the pigeons here!!!!!!
Thank you both for your responses..

I am probably at the stage where I have two choices, either jump on the lathe and knock up a spacer or reheat the case remove and replace the two bearings with Ball type ... I think I need to sit and ponder on this one
 
Steve.S the bearing I used was a NSK N305W ... obviously being unaware of the problem that has arisen my local ball bearing man supplied this based on the sizes I supplied and the application that I described to him also showing him the cutaway picture that is in the handbook .. never mind only a minor hiccup

Endfloat well, I still can't get my head around it.... I've rebuilt many a A65 engine and they have a Thrust face to pull up against, to me the crank on the sloper can float around, I need to stop and have another good read of what literature there is around and maybe I'm over thinking it as I tend to do ... need to sit and ponder a bit on this one too
UPDATE  UPDATE  just pondered and now I see how it works, you need to fit the Cush drive and main nut and Vola everything is locked across to the drive side !!!!! well it made for some conversation hey ??
man, I feel stupid!

Thorntons.. I reckon when I checked their website along with many others when I first started hunting a piston they only showed the side valve one then, so I moved on to alternative ... I spoke with one of our BSA club members and he had fitted the piston I am getting to his engine, and it is very successful, so I suppose I will give it a go, but again thanks for following it up

Timing cover Bush.. I machined a new one of these up as mine was worn , to remove the old one I warmed the case and used a large tap , as it screws in it bottoms out and winds the old bush out , if it doesn't move you need to be a bit warmer, surprising how little amount of heat is required, slip the new bush in and away you go .... thought a seal would be a better option but decided to head with the felt seal as per std.(Chemist has run out of corn pads ) not knowing what clearances I would have. the groove and channel in the bush need to line up with an oil feed hole in the casing. (overthinking again) But? your circlip where is that located? does it just go behind the seal on the crank, no locating groove??

Well, I reckon I've caused enough havoc this morning time for a brew

[chapmast]

The circlip is fitted into the bush - you can see the arrangement in the first picture. The flange of the bush is deeper  than standard to accommodate the oil seal and the circlip. This is why the crank nut needs to be machined so that part of it can sit inside the well.

I tried a similar method to yours to remove the bush, but mine was stuck fast. When I warmed the cover I heard a distinct 'ting' and thought that I had cracked the cover - red crack finder confirmed that I hadn't. At this point I decided that it was safer to drill it out.

The bad news regarding the Cush Drive is that it does not lock the drive side as it is on a taper. Unlike post war models the Cush Drive does not butt up to the Drive side bearing via a spacer. Effectively the whole design relies on the interference fit of the thrust bearing ( i.e. the ball race). If this interference fit has been lost then it could be bad news.

Effectively the internal spacer helps the assembly of the crank. It should be exactly the same width of the external spacer which should be pretty simple to achieve. The spacer effectively ensures that the inner race of the roller bearing sits at the optimum position in relation to its external shell. Without it you would assemble the crank such that the rollers make contact with the lip. It's probably not a particularly big deal as it doesn't really serve the same function as on the post war models. Here the crank is locked by the Cush Drive and the internal spacer is crucial.

Personally speaking it doesn't seem to be a particularly good design and one which BSA would later abandon - along with the 'tiny' engine breather that runs through the drive shaft.