funny speedo

[gavin palmer]

I have a y10 fire 1 litre 1989 model. will problem is if I am sitting still in any gear the speedo shoots right round and then starts to clock up miles very quickley so in a week sitting in my car park my y10 clocked up 400 miles with not going anywhere can anyone please help me I am getting very close to buying £3.00 worth of petrol and a box of matchs thanks

[john orson]

The problem seems to be in the sender unit mounted at the back of the gearbox. It is a sealed unit, but on opening it up nothing apears to be serviceable anyway.