[Rick Parkington]

Agreed David, I think that's the standard place for it. My unrestored '32 9A came with a head steady fitted from there to
one rocker box bolt.
Cheers Rick 

[DavidG]

I used mine to mount a head-steady!

A less obtrusive head-steady mount is the earthing bolt just behind the cylinder head. Make up a straight bar to the top stud on the rocker box. It does smooth things out a bit (even more, I should say!)

[Thomas]

The reason why I dismantled my complete motor were high frequency vibrations visible in the central girder spring (see http://www.marston-sunbeam.org/technicalNotes/model9EngineRebuild.html). Beside that I never had excessive vibration at the head. Vibrations are caused by technical glitches (a worn ball bearing at the crank shaft, for my case). So, I would assume that an extra connection to the frame is not necessary. There is a connection between barrel and frame at my BSA C11, though.

[phutton]

That is the theory, although whether it works is another question entirely!

P.

[Peter 100]

Paul is that to give extra support to stop vibration?
Peter

[phutton]

I used mine to mount a head-steady!

P.

[Peter 100]

Steve and singleminded
Thanks for that it does make sense i never thought of that about the sidecar doh! 😁
Yes there is another under the seat.
Cheers chaps
Peter

[Greybeard]

Its a mounting for a sidecar tube, Peter - most British bikes of 350 or more from the 20s onwards have them. Sometimes used for crash bars or badge bars. Therell be similar mounting point elsewhere on the bike, such as below the saddle, and lower down on the frame.

Steve

[singleminded]

It's the upper front side car mounting lug.

[Peter 100]

Hello everyone
This might be a daft question but what it the hole for indicated on the frame?
I have seen a photo online with something that is chrome plated in one but cannot make out what it is.
Thanks
Peter