The BSA A7-A10 Forum

Technical (topic titles must be descriptive) => Gearbox, Clutch, Primary => Topic started by: mario medeiros on 27.04. 2021 16:22

Title: swingarm gear box roller bearing vs plain casting # 423083
Post by: mario medeiros on 27.04. 2021 16:22
Need to replace my cover as you can see where the cable goes is broken but i see the original cover has the roller bearing and the other cover i have has a plain bearing is it ok just to replace no problem? Should i leave out the washer on the end of the one set of gears that rest up against the plain bearing ? Also does the stamped # 423083 mean this was a scrambler bike? Thanks   
Title: Re: swingarm gear box roller bearing vs plain casting # 423083
Post by: chaterlea25 on 27.04. 2021 22:57
Hi Mario,
Are there letters/ numbers stamped on the top surface of the sandwich plate?
Scrambler boxes would be stamped SC or in your case SCT denoting the Torrington needle roller bearings on the layshaft
I would opt to repair the broken lug, as the identity of the gearbox is signified the lettering on top of this centre case..
The correct lettering has a huge affect on the value of the gearbox and the machine as a whole in some cases
Gearbox types and ratio sheet attached

John
Title: Re: swingarm gear box roller bearing vs plain casting # 423083
Post by: Swarfcut on 28.04. 2021 09:59
 Correct layshaft for this roller  box is plain, no scroll at the driveside end as on standard bushed Swing Arm box. Look in a Gold Star parts catalogue for more assembly details. Thrust washers are required at each end of the layshaft, where a roller bearing is fitted, so the washer shown stays. End float on the layshaft usually taken up by a small hardened thrust washer between layshaft (where the splines end) and large bottom gear H. This washer fits inside the drive dogs on gear F

 A minor repair to the broken lug is the easiest way forward, retaining the benefits of the roller bearing layshaft together with the value represented, as outlined by CJ. Lots on the Forum about gearbox types and things to look out for problemwise.

 Swarfy.
Title: Re: swingarm gear box roller bearing vs plain casting # 423083
Post by: mario medeiros on 28.04. 2021 13:17
HI John
I understand the importance of keeping the original cover but this bike is far from original as i got it.

Hi Swarfy
I am not sure if at one time someone replaced the bushing with the needle bearing on the broken cover but the spare cover i got has the bushing in it and i was just wondering by removing the washer on the end of the layshaft  that my finger is pointing to it should make up the difference in thickness on the bushing that will be up against the layshaft.

BTW also on the case there is a # 42-3003 or might be 42-3005 anyone know what that might be saying?

Thanks 
Title: Re: swingarm gear box roller bearing vs plain casting # 423083
Post by: mario medeiros on 28.04. 2021 14:02
Sorry Swarfy

I was reading your message on my phone and did not see the whole message until I went to my computer.

But if I wanted to use the other cover just don't install the washer?

Thanks
Title: Re: swingarm gear box roller bearing vs plain casting # 423083
Post by: Swarfcut on 28.04. 2021 14:51
 Yes, you can leave the washer out. The gear face will run against the top hat of the fixed bush.  Layshaft  endfloat may or may not require adjustment  with the hardened thrust washer on the inner face of the gear. The float should be minimal, lets hope the combination of bits gives the result you want. More info about Layshaft Endfloat already posted on the Forum.

 Number on the case is the casting number. 42 3006 is the part number for a standard gearbox. Identical castings could be machined differently and require different part numbers. Part numbers and casting numbers sometimes are the same, more often they differ by one or two digits.

 Swarfy.
Title: Re: swingarm gear box roller bearing vs plain casting # 423083
Post by: JulianS on 28.04. 2021 15:05
42 3005 is just the casting part number for the main gearcase.

The needle roller gearcases usually have an altered part number, 42 3072 and 42 3073.
Title: Re: swingarm gear box roller bearing vs plain casting # 423083
Post by: mario medeiros on 28.04. 2021 18:48
Thank you too all.
Title: Re: swingarm gear box roller bearing vs plain casting # 423083
Post by: chaterlea25 on 28.04. 2021 22:59
Hi Mario,
When a standard case is modified at the factory for the needle roller bearing it gets the stamped number next to the cast on one
To identify the gearbox you need to tell us the letters stamped on top as shown on this post

https://www.a7a10.net/forum/index.php?topic=11523.0

John