I wrote an article with Dennis Quinlan about this model, which you can read here. Technically, its a misnomer to call this machine a 'Mk 6 KTT', as the Works models were never labelled KTTs! They tended to have other engine prefixes such as 'M'; the KTTs were always over-the-counter production racers, sequenced Mk 1-8, with the Mk 6 the 'missing link' between the bronze-head Mk 5 KTT and the all-alloy Mk 7 KTT. There never was a Mk 6 for sale, although the factory did build as many as 6 alloy cylinder head racing machines, using modified KSS Mk 2 components. They didn't do all that well in racing, which has always been a bit of a mystery, as the porting and valve size was identical to the 8" square alloy head of the Mk 7 and Mk 8 machines, yet KSS-head racers never produce as much power.
"A 1936 Velocette KTT MkVI racer is now back on display at the National Motorcycle Museum, after extensive repairs to damage it suffered when fire ravaged part of the Birmingham collection in 2003.
With frame number 6TT6, this machine has the long saddle ['Loch Ness Monster', vide Harold Willis] used on Velo racers of the period and carries the race number 74 of the machine on which Austin Munks won the 1936 Junior Manx Grand Prix, although it is not known exactly which of the very few MkVIs this is.
The rebuild by a leading Velocette specialist included a conical rear hub correct for the year, but not fitted before the fire. Unfortunately but not surprisingly, the original crankcase was unserviceable and has been replaced by a new casting in the Stanley Woods-inspired short wheelbase 1936 frame."