ts 250 gearbox problem

[bryvw1973]

hi
i have been restoring a ts250 with side car for the past two years and it was nearly there until last weekend,
it fired up for the first time in many years it was an emotional moment,
but then i decided a small test ride was in order so i pulled in the clutch popped it into gear and was greated with a cracking noise then no drive and cant select gears,
i was gutted lost heart big time,
so the question is does anyone have any idea what the problem may be?
any help will be appreciated as i dont want to sell it as an unfinished project
cheers
bry