Hi folks, as previously mentioned in the other Warzone Speedway thread, have been a follower of speedway and grass track since knee high to a grass hopper, came across this photo last night in an album ( knew it was somewhere ) with me sat on my uncles bike with my brother and dad by the side. Worked it out it must be around 1965/66. 
email (option): ianhince@tiscali.co.uk
If it's a Speedway or grass bike from that era my guess would be a JAP...Ian
email (option): ian@wright52.plus.com
I reieved my copy this morning..a quick look through it indicates it will be a good read...Thanks Dave...Ian
email (option): ian@wright52.plus.com
Well, Ian`s bang on the money, yes it is a JAP, these are still being used today in the Pre 75 and upright classes. 
email (option): ianhince@tiscali.co.uk
I homed in straight away on the section in the book covering the bikes themselves..and a common conversion in the early days was to put a Matchless top end onto the 16H bottom end. This was no doubt done to bump engine capacity to 500cc.
A few years back I was at a scrambles meeting and there was an M20 there with a Matchless top end fitted.
With its steel flywheels (cast iron in the 16H I believe), more suitable and better lubricated big end I would have thought the M20 more suited as a donor for an engine that was to be modified for competition use.
However, at least in this book, that conversion is niether pictured nor mentioned.
Unfortunately I didn't find out what year the Matchless components used on the M20/Matchless originated from.
One of the key things with these conversions is the spacing between the tappets and the offset of the tappets from the centerline of the engine.(for alignment of the pushrods)
Can anyone out there with a WD Matchless in bits provide me with these dimensions?...It might answer the question as to why that particular conversion does not appear to have been built..or maybe those old boys did actually believe some of Nortons racing technology was actually applied to the 16H!.Ian
email (option): ian@wright52.plus.com
I saw another interesting picture of a 'special' today, brought along by one of my customers...an M20 bottom end fitted with a cylinder and head off a Harley Davidson 'iron head' Sportster...Ian
email (option): ian@wright52.plus.com
Hi Ian, Trevor showed me some of the pictures of bikes used in the book, the Norton/Matchless conversion was the one that took my eye. Just brilliant engineering skills
email (option): horror@blueyonder.co.uk