going backwards...

Strange one this- my RB225 has started playing up. Took it out yesterday for the first time in six months, three miles down the road and the engine dies on me, roll to a stop and its ticking over nicely, pull away again and it will not rev past about 1800rpm, ie 30ish mph. Engine cools and its fine for another three miles then the same thing happens again. Go home. Strip and clean carb (34mm dellorto) all fine. Tried new plug, cdi and fresh fuel.
Took it out again this morning, all fine for three or four miles then it starts again, stop on the side of the road, check a few things then put it into first, drop the clutch the bike goes.......BACKWARDS......
. Back into neutral, scratch head, back into first and off we go, 30mph, splutter splutter.... HOME.
Stator? timing? help !
Took it out again this morning, all fine for three or four miles then it starts again, stop on the side of the road, check a few things then put it into first, drop the clutch the bike goes.......BACKWARDS......

Stator? timing? help !