Please - A B31 Question

[BSARGS650]

Please forgive me; I know this great friendly Forum in the cosmos is about the twins, but, as there is so much expertise amongst this community, I have taken the liberty to ask a question about the single half brother of the same BSA family.

I am looking to put together a B31 engine that was stripped down countless years ago and starting to gather information; service sheets, spares catalogue and sorting out what parts I have, or what I have not.

My question relates to the crank set-up.  There is a spacer, which I can't find at the moment, that sits between the drive side bearings, no shims apart from some outer ones of various thickness.  It appears that the spacer is of a standard fixed length, no options of different size.  The Service Sheet 305 seems a bit vague on assembly, it may be I am loosing the plot these days?  Please, does anyone have the dimension for the spacer?  How is the crank/rod float set up for alignment with the centre of the barrel?

My sincere apologies if I have offended anyone with this B31 question and will duly punished myself.  If it was not for this dastardly virus lock-down, I would sentence myself to being in a locked room for an hour with Lady Nugee, Ms Soubry and Ms Sturgeon, or a half our lecture by Ian Blackford, or 10 minutes with Ant and Dec, but none of this is possible.  I will resign my suitable punishment to listening of 24 repeats of Tulips from Amsterdam by Max Bygraves.

I would very much appreciate any advice, and I thank you in anticipation as I may not reply in a timely manner expected - I will be looking for missing parts.....Kind regards to all of you.

[Klaus]

As I still remember its the same spacer.


http://www.wdbsa.nl/download/BSA%20bearing%20distance%20piece-Model.pdf

cheers klaus

[KiwiGF]

Please forgive me; I know this great friendly Forum in the cosmos is about the twins, but, as there is so much expertise amongst this community, I have taken the liberty to ask a question about the single half brother of the same BSA family.

I am looking to put together a B31 engine that was stripped down countless years ago and starting to gather information; service sheets, spares catalogue and sorting out what parts I have, or what I have not.

My question relates to the crank set-up.  There is a spacer, which I can't find at the moment, that sits between the drive side bearings, no shims apart from some outer ones of various thickness.  It appears that the spacer is of a standard fixed length, no options of different size.  The Service Sheet 305 seems a bit vague on assembly, it may be I am loosing the plot these days?  Please, does anyone have the dimension for the spacer?  How is the crank/rod float set up for alignment with the centre of the barrel?

My sincere apologies if I have offended anyone with this B31 question and will duly punished myself.  If it was not for this dastardly virus lock-down, I would sentence myself to being in a locked room for an hour with Lady Nugee, Ms Soubry and Ms Sturgeon, or a half our lecture by Ian Blackford, or 10 minutes with Ant and Dec, but none of this is possible.  I will resign my suitable punishment to listening of 24 repeats of Tulips from Amsterdam by Max Bygraves.

I would very much appreciate any advice, and I thank you in anticipation as I may not reply in a timely manner expected - I will be looking for missing parts.....Kind regards to all of you.

I have also asked questions regarding a b31 in the past, its certainly “allowed” ....and several members including me also have b31s so know a bit about them, but there is section for non A7/A10 questions and when admin get around to it your post will probably get “moved”    

[chaterlea25]

Hi RGS,
The drawing provided by Klaus is correct for the B31, the length is a critical measurement and both faces must be perfectly parallel
It needs to made from a tough steel, I have seen a lot of them with hammered or worn ends. I made replacements from EN24
There is a "shim washer" that fits into the recess of the drive side case before fitting the ball bearing
This acts as a labyrinth seal between the crankcase and primary case
If shims are needed to centeralise the crank they need to be fitted next to the oil slinger inside the roller bearing
Be careful not to move the crank too far to the timing side as the bearing rollers could get pinched endways
Before fitting the cush drive assembly there should be a minimum of 10/12 thou end float on the assembly
The shims shown in the parts book are to align the primary drive

John

[BSARGS650]

Many thanks for taking time and patience for your most welcome and informative replies of which I will take note.

It looks like I have found what may have been the spacer?  It looks to be of size, but with mushoomed ends, as noted in the replies!  I swear it looks like a piece of old galvanised pipe.  I notice in the specification drawing, the material is mild steel, but have noted the suggestion that it should be of EN24.

For crank alignment purpose, the shim that accommodates this process, I take it that the oil flinger sits next to the crank, then the shim (if required), then the bearing.  I presume this shim needs to be made as I don't see any of various thickness in the parts catalogue.

Interesting replies, thank you again.  I have smashed the old Max Bydraves record of Tulips from Amsterdam, it drove me mad.  And, thank you Moderator for allowing my intrusion into this most revered, respected and helpful BSA A10 Forum in the cosmos.

Kind regards to all.....

[muskrat]

Flattery will get you everywhere. 
Cheers

[chaterlea25]

Hi RGS,

but with mushoomed ends, as noted in the replies!  I swear it looks like a piece of old galvanised pipe.

Yup 

In a lot of B31/3 engines the drive side roller bearing has a lip on the outer race, if the spacer is less than 1.000in then the engine will lock up when the cush drive nut is tightened
Been there done that with what looked like a usable spacer

From memory I was given the material recommendation by a well known Gold Star Engineer,  He makes his own spacers increasing the outer diameter to the size of the bearing inner races

I take it that the oil flinger sits next to the crank, then the shim (if required), then the bearing.  I presume this shim needs to be made as I don't see any of various thickness in the parts catalogue.

Correct

The shims (if) needed can usually be found in an engineering supply shop or cut from shim stock
BSA's were quite well made and tolerances were kept tight, unlike other marques who made up for poor engineering with shims (now the  starts  )

John

[Klaus]

Hi RGS

The shims are for to center the crank in the case. When assembling you can fit the drivesidecase only on the shaft with a locked cushdrive. So you can see if the conrod is in the middle of the barrel the other half with no bearing is bolt on.
If any shim is need it is easy to split.

Klaus

[BSARGS650]

Many thank to the most recent informative contributors to this topic.  I am surprised that no "conventional" type of seal prevents leakage of engine oil from the drive shaft into the chaincase, relying on a shim/labyrinth arrangement to do the business.   Please, may I query the end float minimum of 10/12 thou?  Should this be a maximum?   Many thanks again for all the advice given - I knew this would be the right place for patient and expert help......and it answers all my questions raised.

Kind regards to all.....

[chaterlea25]

Hi RGS,
10/12 is the target figure, I would not go less than 10 or more than 15
With larger endfloat the timing side bearing inner and outer go further out of line
With less endfloat the timing side bearing rollers can get pinched endwise from expansion
If there is excess end float after getting the conrod central then shims can be added inside the timing side bearing
Remember to work the conrod from side to side on its end float when checking if its central

John

[BSARGS650]

Many thanks John for clearing that last query.  I have to say, I learnt more from this forum expertise about the B31 engine set-up in such a short time than I could read elsewhere.

Hell, this is the place to be......sorry, I meant this forum.

Best regards to all.....