Originally Posted by Shandy

I've got one of these and have had the same problem in the past. It was when i had a connection problem on one of the coils and a wire had fallen off causing the bike to run on one cylinder.

It sounds like your bike is running on one cylinder, the rev counter takes its signal from one of the igntion control units, if it drops to one cylinder, no singal to go to the rev counter.

This could be anyone of a number of things from,

Spark plugs, HT leads, ignition control units, pick ups or coils. Or it could be as simple as mine was where a wire had worked loose and eventually fell off.

I'd check all the wires are connected where they should be, then as Kato sugested swap things about and by a proccess of elimination until you should find what broken.

Hope this helps, good luck,

Shandy