rev counter/low power/electrical/jerking

Hi
I was wonderig if anyone could help me out. I have 98 regd. M600. It has a rev counter fitted to it which was on it when I bought it and its worked fine up till now. Its a carbon look type, which incorporates the speedo and has little red lights that go round in a semi-circular motion as the revs increase.

When the ignition is turned on the lights on the rev counter illuminates all the way round in a semi circle and then comes back and rests on idle. However, what has recently happened is that sometimes no rev counter lights come on at all and other times the rev counter lights come on and just stays on.

Also, there's a severe lack of power. Almost feels as if its running on one cylinder. Not sure but I think perhaps the problem rev counter may be affecting the bikes performance. The problem started in the summer, so I don't think its the cold weather that's causing the lack of power.

Although the bike has recently been serviced it still doesn't feel right. It doesn't have any power and jerks as its revved. I managed to get it home, which is approx. 60 miles away, in miserable conditions, but it was jerking and kept cutting out at traffice lights etc.

I've since phoned up the garage that carried out the service and they said it may be the 'Kookazans' which I've never heard of it. It apparently sits under the battery.

I'm not sure if the problem with the rev counter is affecting the power delivery and causing the power loss and jerking. I'm reluctant to take it back to the garage where it was serviced as I've already parted with £380.00 and can't afford to cough up more cash.

Any assistance would be grately appreciated. I'm in Brighton/Hove. Thanks.

[Gadget]

Try changing the spark plugs. My bike ran like you are descibing.
Changed the plugs and she ran smoothly after. I do not know why but it has happened on both my monsters both times new plugs have sorted it.