BSA Owners' Club Forum

The BSA Workshop => Twins => Topic started by: Oily Al on 24 August, 2017, 23:05:23

Title: Crankshaft. Oil pump drive pinion L/H thread.
Post by: Oily Al on 24 August, 2017, 23:05:23
Dear Enthusiasts, Could anyone help me with a problem I currently have with a badly butchered L/H thread on the timing side of
my A65 Thunderbolt 1971 OIF basket case restoration? The end of the shaft seems to  been repeatedly struck and has belled out, to the point where the lockwasher slot has split. I would like to know what the description of this thread is and wonder if it is possible to get hold of a die to clean it up. Hopefully it is repairable, but if not, has anyone got a good late OIF crankshaft within tolerances? I have an excellent late Lightning crankcase if anyone is interested, too. Many thanks.     
Title: Re: Crankshaft. Oil pump drive pinion L/H thread.
Post by: JulianS on 25 August, 2017, 10:37:59
Thread is 9/16 x 20 tpi left hand cycle.

Unfortunately some people bash the end of the crank to get it out rather than use a puller to remove the crankshaft pinion.

The danger is that the end of the crank is slightly bent especially as, from your description, it appears a lot of force was used.


Title: Re: Crankshaft. Oil pump drive pinion L/H thread.
Post by: Greybeard on 25 August, 2017, 14:33:13
Don't you just hate it when you come across something like that? If it isn't too bad you may be able to rescue it with either careful use of an appropriate thread file, otherwise a die may clean it up.
Give tracy tools a ring or trawl their website. They do stock a huge range of taps and dies. For rescuing a damaged thread a carbon steel die will be adequate - and much cheaper than high speed steel.

Steve
Title: Re: Crankshaft. Oil pump drive pinion L/H thread.
Post by: Mike Farmer on 25 August, 2017, 19:20:40
 :)

 Ho Ho Ho. Mine had the locknut welded on. Oh what fun. Oh what joy. I'd like to strangle whoever did it. It was only because someone had gnurgled the LH thread locknut. Fortunately it was only two or three largish 'splashes'.
I hope the cretin who did it is reading this.

Mike 8)
Title: Re: Crankshaft. Oil pump drive pinion L/H thread.
Post by: Mike Farmer on 25 August, 2017, 20:47:57
 :)
Hi agen.

I'm just going to throw this one in because I have no way of checking it out. Where problems have arisen on the crankshaft end like mine having been welded, from that point on it is suspect.

So your thoughts on this one: Would it be possible to drill and tap the crankshaft end and put a keeper stud in. RH thread so that any attempt of the locknut to turn would automatically have a tightening affect on it. Should be able to do away with the lock washer.

As I say I have no way of checking this so your thoughts please. Then should mine fail I have some idea where to go with it. Might be of use. Even if a hollow plug was used>>>>>

Mike 8)
Title: Re: Crankshaft. Oil pump drive pinion L/H thread.
Post by: Oily Al on 26 August, 2017, 02:42:44
Dear All, many thanks for the swift replies on this thread. I'll check the damaged end of the crank on the lathe for trueness first and then see if I can get the appropriate die/thread file. Thanks,Julian S, for the technical information. What surprised me was how soft the metal is at that point on the shaft. Fingers crossed for a successful recovery job!
Title: Re: Crankshaft. Oil pump drive pinion L/H thread.
Post by: Oily Al on 20 November, 2017, 00:08:09
As a postscript to this subject, thanks to members advice and replies I have a hopefully happy result regarding the crank.
I bought a 9/16 L/H cycle thread die from RDG tools (Excellent service) and mercifully, the knackered thread cleaned up very nicely.
What staggered me though, was the amount of sludge in the crank. I think that the threaded plug had defeated previous owners from removing it due to very heavy-handed peening, so as you see in the photo, I'm glad that I persevered.
Many thanks again.