Hi Jon
There is no real way of dating the TY80 as they were made 1974/5/6 and 1984 onwards and if it is a Whitehawk it will be a 1976 build.
It sounds like a Whitehawk and if it is it’s a very desirable piece. There were 2 models of Whitehawk the first one had 16” rear and 18” front wheels, the later one had 17” rear and 20” front both used a rather agricultural ally front fork extension at the bottom that pushed the spindle out a bit.
The engine on the Whitehawk was no different from the TY80 and the forks, apart from the extensions were the same, otherwise everything was changed.
If you go to
www.twinshocktrials.co.uk, join and go to the photo’s section you will see the brochure picture of the later model.
Great little bike and very much in demand, in fact if you want to sell I can put you in touch with a buyer.
Anything you want for it or any advice just give me a call.
Cheers
John