Author Topic: Crank bearing/bush timing side. Part No: 65-2052 Query  (Read 426 times)

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Online Owen

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Re: Crank bearing/bush timing side. Part No: 65-2052 Query
« Reply #15 on: November 24, 2021, 10:26:23 PM »
BSA service sheet 702 gives the bush ID as 0.983 - 0.982
1940 C12 (350cc)
1945 C11
1953 C10 & C11

Online Goldfinger

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Re: Crank bearing/bush timing side. Part No: 65-2052 Query
« Reply #16 on: November 24, 2021, 10:42:09 PM »
Marvellous, thanks everyone - it's actually within spec. That's saved me a lot of time and expense :-)
The internet can be corrosive used inappropriately but to have a site like this, with expert advice on hand, is invaluable.
Regards
GF
« Last Edit: November 24, 2021, 10:46:40 PM by Goldfinger »
1957 C12
Sheffield

Online timsdad

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Re: Crank bearing/bush timing side. Part No: 65-2052 Query
« Reply #17 on: November 25, 2021, 07:56:38 AM »
In my comment I mentioned that the bush is not so critical because the C11 has a roller bearing big end, that only needs a minimum amount of oil to keep it lubed. The roller main also only gets a splash at the best of times.  It's the big twins and unit-construction Bs and Cs that need a far better oil supply for their plain big ends.

Any decent workshop can ream a new bush to correct size, and I have reamers from about 1/4" to about two inches from my truck repairing days. It's a little bit more involved to ream a new bush in line with the other main bearing if your tapered guide won't reach across the pair of cases bolted together.

Ray
Just a motorcyclist.

Online chaterlea25

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Re: Crank bearing/bush timing side. Part No: 65-2052 Query
« Reply #18 on: November 25, 2021, 10:08:28 PM »
Hi All,
Oops!! my memory failed me (again) on my 1in. reply :-[
0.982 is as near as dam to 25mm ... 0.06mm less

Some years ago I remember getting a 10thou under size bush from C&D for an engine where the crank was worn
I had to true up the worn part in the lathe very carefully  ;)

John

Offline izenoze

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Re: Crank bearing/bush timing side. Part No: 65-2052 Query
« Reply #19 on: November 28, 2021, 11:46:21 PM »
As to how long an engine can run with a clapped out timing side plain bearing (technically it’s not a bush as a bush, by definition, does not have 360 degrees of rotation), well my engine when dismantled had a very large clearance indeed. So large that the flywheels were no longer perpendicular to the bore. This meant that every power stroke the connecting rod was thrust to the timing side. So much so that over time the land on the connecting rod wore a 0.020 deep groove in the RH flywheel. There was no sign of overheating on the rod

This made it difficult to get the sideplay right when I rebuilt the engine. The groove was machined out concentric to the crank pin hole, this involved mounting the flywheel in a chuck by it’s shaft and mounting the chuck in a bigger chuck. A bronze disc was then machined up to fit the recess

The bearing must have been worn for a very long time yet the timing gears seemed to have suffered no ill  effect. Of course the gears may have been changed at some point as it’s operational history is unknown. Must have made an awful clatter but as the roads are mainly dirt, potholes and loose stone in Fiji I guess the owner didn’t hear it or didn’t care