Emerson's Brooklands ABC Sopwith - a question?

In the attached picture Emerson's ABC looks to have a much longer timing case? What are the differences from the standard ABC Sopwith engine? Also did he run with a shorten/stiffer front leaf spring? Appreciate your knowledge
regards
ian

Keith's bike has a shorter front leaf spring. Never seen it anywhere else. Maybe it was made for racing only.

Hi
Giovanni have you noticed in the photo he has one white tyre and one black tyre ?white tyres were used before the war and black after. It's probably ex stock ?

Any idea when Emerson's picture was taken?
It could be that original ABC's only used white tires. On my skoota, foot rest rubber is white inste although very dirty outside. Tires had to be white.
Even looking at catalogue pictures like the one on the homepage of this website, original tires were white

Iàm not sure when white became unpopular and was replaced by black rubber only.

There is a drawing of the early engine in The Motorcycle Dated march 13th 1919 which shows clearly the extended timing gear case.

Hi
To answer the question: where was the photo taken? Here is some more information.
There is a zoomed out version of the image stating it is at Brooklands at the imagelink below:

http://www.stilltimecollection.co.uk/detail/2844-abc;-bike;-brooklands;-racing;-tpt-abc-398cc-set-500cc-hour-record-of-70-miles-distance-etc-see-look-observe-page-37-vyab-jack-emerson.html

I’ve convinced myself that this is correct as it looks like the same place captioned “Brooklands 500cc 1 hour race, 29th May 1920” on the imagelink below:

http://velobanjogent.blogspot.co.uk/2011/11/early-motorcycling-photosbought-for-me.html


I’m guessing that it is the finishing straight. What do other people think?
Regards
Neil