Watch it 4stroke, your question might start a Trialscentral forum pre65 rant!
Some of the bantams will only use the original engine bottom end & cylinder head. Everything else is new, or recycled parts from newer bikes such as forks & wheel rims.
Have you got the chain adjuster as far back as possible. You might be able to move the wheel back to gain some more wheelbase. To do this you will have to add a link or 1/2 link to the chain.
Condolences to his family. I was one of the many who remember him from enduro's, he would usually be in the remotest place manning the quickest check, always ready for a some banter when having your time card marked.
I did events all over Britain, he was always there. You always knew it was him the timing clock had a cover on it that said oy wot time is it
Engine weights
in Yamaha
Posted
'A' models had aluminium engine outer casings.
Later models had lighter magnesium alloy casings.