Can anyone advise where i should start looking, history is as follows.

Bike has been fantastic untill this afternoon, trvelling along nicely at 60mph when bang!, something happened, the bike still ran, but the rev counter started jumping about from 2K to 10K eratically.

On the way home the Rev counter is still doing its wierd thing, also the temp guage goes back and forward then settles. Then..

Backfires, and the engines cuts out. stuck on side of road for 15 mins then it starts again, rev counter still wiered, but bike runs for 1/2 mile, then backfire and dies.

Ride like this to get home for next 4 miles, stop/start/stop/start etc...

Any one got any ideas where to start looking first?

Regards

Rich