crankcase repair options

[shoal48]

Good afternoon all, Im just in the process of sorting out all the bits for a long dismantled '61 C15. The previous owner, for some reason, had started reassembly using a different RH crankcase so I'm rebushing the  original RH crankcase, restoring a few threads etc and came across an unexpected problem.

The inner end of the gear selector quadrant assembly is located in a blind hole at the back of the gearbox. The outer end obviously going through the inner and outer covers to the gear lever. It would seem that the blind hole in the casing had become worn and at some point an alloy sleeve had been inserted and then redrilled. The problem is that they drilled right through the casing into the flywheel area.
Clearly this is a no no as crankcase compression would push engine oil into the gearbox and gear oil would seep back into the main crankcase.

I have been pondering about the best way to plug the unwanted hole. My first thought is to tap a thread in the last 6mm of the hole, thread a piece of alloy round bar stock to make a grub screw then screw it in with a bit of high temp epoxy & peen the edges to stop it ever coming out.
Another possibility might be to knock in an alloy plug & get it TIG welded in.

Has anyone had any experience with this sort of repair and can you advise which is the best option, or indeed, suggest a better option.

[idie]

If it were me I would use a piece of alloy sheet and fix over the hole using something like JB Weld. Once tried that won't come off.

[DAVE BRADY]

Hi,

Threaded grub screws are used on several BSA models to blank off oil way drillings with good results.

Dave.

[shoal48]

it seems we are all on a similar page with this, welding is probably over the top. Thanks for the comments, very helpful.

 think I will tap the end of the hole, screw a suitable bolt in, coated with JB weld, then grind it off flush with a dremel, and maybe stake it for good luck This project is like an archaeological puzzle, trying to work out why the original owner did certain things...2 sets of crankcases, 2 heads, 1 barrel but 3 pistons, only I set of gears, distributor but 2 and a half flywheel sets   Hopefully I will be able to fix the hole and get the seals and bearings in this week.

[shoal48]

all sorted thanks. Used M10 tap to put thread into last 5mm of hole, cut off 5mm from M10 bolt, slotted it and screwed in flush. Will fix permanently with JB Weld once once I've fitted the new bushes as don't want to heat stress the epoxy unnecessarily. 

[JulianS]

As an aside it appears that the early C15 cases were drilled right through.......

[MadPete]

That is why I love BSA. "Existing quadrants can be modified by turning a grove..." Those were the days when we were taught metal work and wood work at school. "What do you mean you don't know how to turn a grove?"

...my metal work teacher will be turning in his grove as I write.