What have I broken

Hello everyone and Help!!! Recently bought a 1971 Dax, all was running well until bang crunch crash hahaha, I will try & explain. Riding down the road about 15-20mph, a nasty grinding / crunch noise, pulled over turned the bike off. Into neutral re started fine, 1st gear and set off slowly, all fine until I started to speed up or give it work to do like up a hill . It sounds like cogs grinding or chain slipping, I have ruled out the chain slipping so suspect something inside the gearbox or clutch. What do you guys think?

Don't take a chance, strip it! It is pretty straight forward. A copy of Haynes Honda C50-C90 will help you as the engine is the same as the ST. Found my copy on the net for £2.50. Worth it's weight in gold.
Pete.

Thanks for that, I will clear some space on my bench and strip it down. No doubt I will be back for further help.