Author Topic: 1947 B33 Crank case assembly help needed  (Read 476 times)

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Mr P

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1947 B33 Crank case assembly help needed
« on: 17 May, 2024, 21:25:37 »
Hi.  I have a 1947 B33 and have stripped the engine as the splined inner cush drive bearing (65-2523) is rubbing on the engine case.
I am unsure of the correct assembly so would appreciate some guidance / help.
It seems  the Cush drive bearing needs to be further away from the crank case.
It was assembled as follows from the inside to out: on crank shaft drive side the it goes: oil flinger (24-2113), inner roller Bearing (24-722), Distance collar (66-660), Spring ring, outer Ball Bearing (65-2045) , washer / Shim I suspect this is 66-661 which appear to come in many different thicknesses. lastly the cush drive bearing (65-2523) was fitted to the shaft on the outside of the case.
The Draganfly preunit B group does not show a washer / shim between the ball bearing and the case.(https://draganfly.co.uk/product-category/bsa/sparesparts-for-bsa-a710-b3133-c101112-m202133/engine-gaskets-gearbox/crankcase-abcm/pre-unit-b-m-group/).
Q should there be a shim/washer or not?
Any ideas how to stop the cush drive rubbing on the case and how to set the end float?
Should there be some kind of distancing collar or washer between the bearing and the cush drive bearing? e.g 66-1705.

Please help me to bring this lovely machine back to its former glory. See attached .pdf for pics etc Very Best Regards Mr P
« Last Edit: 17 May, 2024, 22:03:29 by Mr P »

neil1964

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Re: 1947 B33 Crank case assembly help needed
« Reply #1 on: 18 May, 2024, 00:17:13 »
Sounds like you are missing the cush drive distance piece 65-2528 that goes between the inner race of the ball bearing and the cush drive bearing.  Yours is presumably tin casing and 4-lobe cush?

I think the shims go between the bearing and distance piece when aligning with primary drive. 

For swing arm models with alloy primary case this spacer is 42-42.  I only have s/a machines and 2-lobe cush, but can measure 42-42 for you if needed.

idie

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Re: 1947 B33 Crank case assembly help needed
« Reply #2 on: 18 May, 2024, 03:06:26 »
Sometimes the splined sleeve has the spacer built on . The spacers come in different sizes. Around 12mm thick.

Mr P

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Re: 1947 B33 Crank case assembly help needed
« Reply #3 on: 18 May, 2024, 08:20:36 »
Thanks for your help I will try to get  a 65-2528. Yes it is a tinware primary drive case (stopping that leaking will be a later challenge). Yes it is 4 lobe cush drive, I had guessed a spacer maybe needed and thought about making a phosphor bronze one. If you could give  me a thickness of 42-42 that helps to build a picture. I suspect minor mis alignment can be accomodated by the primary drive chain. Thanks again for your help. I will remove that shim washer from behind the bearing in the case as it seems that should not  be there.

Mr P

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Re: 1947 B33 Crank case assembly help needed
« Reply #4 on: 19 May, 2024, 13:11:46 »
Hi I think I discovered the  problem. According to the BSA catalogue of genuine spares 1947 The correct cush drive splined hub for a 1947 B33 comes with a built in spacer.
65-2534, (https://pesltd.uk/?products=gearbox). It is also the part for 1947 B31,B32,B33, B34, M20 and M21.
Draganfly list a 1947 B33 part as 65-2523 (https://draganfly.co.uk/shop/72655/sleeve-engine-shock-na/#65-2523Usleeve-engine-shock/category_pathway-2?Itemid=505) which does not include the spacer.
I guess as you suggeted just adding the spacer will solve the problem, or I could get a new 65-2534.
If anyone has a 65-2534 and can measure the built in spacer depth that would be useful.
So the way my engine was assembled was correct except that it had the wrong cush drive splined hub, and no alignment washer 66-1707 or 661708 was fitted on outside of crank case between the cush drive splined hub and 66-661. Anyway I hope this helps anyone else as I have seen other people post similar problems.
This is link helps explain things https://www.britbike.com/forums/ubbthreads.php?ubb=showflat&Number=547680
I have also attached .pdf which should make it obvious. Best regards to you all Mr P.

Steve.S

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Re: 1947 B33 Crank case assembly help needed
« Reply #5 on: 19 May, 2024, 15:03:02 »
I see no reason why you can't just make up a mild or stainless steel spacer of a thickness to allow the engine sprocket to line up with the clutch sprocket. I don't think you need to use Phosphor Bronze.

idie

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Re: 1947 B33 Crank case assembly help needed
« Reply #6 on: 19 May, 2024, 17:19:49 »
I would put the splind sleeve and sprocket on loose. Use a straight edge alongside the engine and clutch sprocket measure the gap between the sleeve and bearing. This will give you an idea the thickness the spacer needs to be.