What the heck is this ?? "Mystery bolt" on my 1956 R-26 drive shaft housing

[schrader7032]

It looks like your driveshaft for the R26 is enclosed, meaning there should be some gear oil in there for lubrication. Wouldn't this be where you put the oil? It doesn't look like the standard spot though...usually it's a bit further back on the square housing just before the joint with the final drive. Plus the plug doesn't look anything like the plugs I've got on my R69S...mine is a standard hex screw head, not domed and/or brass like yours. My R25/2 has the exposed Cardan shaft...did they switch to the enclosed driveshaft for the R26? Here's a picture I found but it's hard to tell if there's a fill plug...maybe there's one on top, but it sure doesn't look like there's one where yours is:

http://www.bmbikes.co.uk/photos/photoph ... %20(4).JPG

Well, it's at the bottom of this page, anyway:

http://www.bmbikes.co.uk/photopages/photosr26.htm

My R69S does have an electrical connection with a flip cap located under my seat. My R69S with Earles fork has the lugs on the right side for a sidecar.

[Grant R26]

My 1956 R-26 has an inspection bolt on the drive shaft housing...just like the filler plug on the rear end.

No idea what it is for as there is no lubrication at the point as far as I know.

my 57 R-26 does not have this and similarly my R-27 is entirely bolt-less in this area

Any ideas what it is there for ?

Could it be side car related? This bike was definitely fitted at one time with a side car. The imprint on the paint under the seat is clearly visible.

and there is an electrical outlet under the seat with a watertight flip up lid that I assume was where the power to the tail light on the side car hooked up.

Could this bolt hole have been something to do with the side car mounting ? Some kind of anchor point for the sidecar hardware?

I assume this is not original to the bike from 1956 ??

Thanks

Grant in Toronto