i had one of those thirty years ago

got it cheap had blown motor

fitted rt360 yamaha engine in
adapted down pipe (easy)
ran cz rear sprocket (huge)

it was the best trail bike in our group
would climb any hill

only drawback went from first to fifth
very quick (see sprocket)

ended up trading in on a rm250b at clipstones yamaha ringwood
fug knows what happened to it
i remember the motor went in very easy (weekend job)
and shit it was loud

i will have a look might have a photo somewhere
