As above, My brother has told me that when he tries to engage reverse the box gives out a whirring sound but does not engage just jumps straight back out?
Gears 1 through to 6 are fine.
I know it's not down to the clutch as It had a new Helix plus skimmed flywheel about 4k ago.

Anyone have any ideas??

 

is he lifting the tab for reverse ? he isn`t just trying to select it with the clutch down is he ?

 

No. I did ask him that at first but he assured me that he has been using the tab.

 

Wonder if the cable for reverse has come off the box Does it try and go into reverse or is it locked out?

 

Have just spoken to him and he tried it while on the phone. It just grinds but won't engage.

 

Doesn't sound like the cable then