Mystery chain case hole '54 NH

[dennis.t]

I have a hole in the primary chain case of my '54 NH and I do not know what it is for.
The hole does not appear to be threaded.
See the photo with the hole highlighted next to the clutch chain sprocket.
Any advice is welcome.
Many thanks,
Dennis

[Simon.Gardiner]

Looks like that's the chaincase inner for the bikes with the FERC, that hole has a small bolt to attach to the tab on the FERC front section.
Compare the back of that inner (around the gearbox sprocket) with the one on your VH. (I suspect the battery carrier mountings are different also?)

SG

[Roger Gwynn]

Yes, the battery carrier mounts are at a different height and there is not a wall around the gearbox sprocket. I notice you have a 1958 engine number!

[dennis.t]

Thanks both. The bike is a bitsa so parts and the engine span several years. I am not fitting a FERC so I will blank off the hole. It is good for me that many parts span many years and are largely interchangeable. I have been caught out by some exceptions e.g. the fork leg mudguard mountings but I can generally work around those problems.
Regards,
Dennis

[Mick D]

Hi

There is a tab washer that locks that bolt normally, I suggest you fit one if you are going to blank it with a bolt, last thing you want is a loose bolt in the chain case.

Regards Mick

[dennis.t]

Thanks

[paul.jameson]

I wouldn't use a bolt to block the hole. Just clean the hole out and fill it with a bit of silicone. If the silicone does eventually come out it will do no harm at all.

[Simon.Gardiner]

Or araldite a square of beer can over the outside?
One such has been serving me well for many years (I don't use the bolt even with the FERC)

SG

[TonyBaxter]

Hi

There is a tab washer that locks that bolt normally, I suggest you fit one if you are going to blank it with a bolt, last thing you want is a loose bolt in the chain case.

Regards Mick

That was me in 2022 riding to Paris for Vintage Revival Montlhery that year. Ended up with the primary in bits on the floor after the bolt holding the inner to the engine came loose. Picture is just as I had got it all back together again. Took another four hours to get there, arrived midnight after a hairy no-lights blast along the motorway

[Roger Gwynn]

Where is the crowd of onlookers offering help and asking dumb questions?