Re: Wheel tracking with sidecar

 
In my BMW anyway, there are spacers between the engine
and frame on each side and the swingarm is centered in the
frame by means of 2 pivot pins. Assuming that you have any
clearances to work with, perhaps you could stack everything
as far to the right as possible.

I'd speculate that you might be also be able to offset the swingarm
perhaps 1/4" to the right of normal in relationship to the engine,
though I'm not 100% sure of this in a single U joint drivetrain.
You could probably get away with this on a Paralever.

Plan B might be to truck the swingarm over to a machinist/welder
and hack at it a little to narrow the swingarm. Width of the engine
mount studs (the ones which run through the engine and frame)
should be about 300-325 mm. YMMV.

You can find parts fiches for most airheads here:

http://www.ascycles.com/illustrated_parts_catalog_main.aspx

The studs are called out as "pin" and a length usually follows.
Good reading anyway, as you get some idea what you're working
with.

I like this plan better than the chain driven Spagthorpe replicas.
Had you considered transplanting Dnepr components onto an
R75 instead ? :-)

 
The offset actually works out better than having the wheels in line.
It helps keep the sidecar wheel down compared to having the wheels in
line.  As for the lean angle it doesn't seem to make much difference.
I have a variety of sidecar tires that vary up to 2" in diameter.
That varies the lean angle by a few degrees.  Hardly notice the
difference from one to another.  The toe in does make a difference.
Try for near zero.  Changing the tire dia wont affect that.