ok had stator back from spain put it on fired up after 2 kicks running nice

let it warm up fan comes on and runs but when i rev the bike the fan slowws right down but if i let it tick over the fan is at full speed any ideas

Sounds like the Fan Module is hooped.

hi were is the Fan Module and whats it look like new to these trial bikes there aint a lot of wiring on them lol

Just an idea that might be worth a go... eliminate the sender and try it again.

Simply disconnect the two wires and join them together.

It's an easy thing to do and costs nothing but just might point you in a different direction, if the fan then runs at a constant speed the sender or the connections might be breaking down under load/ vibration.

tryed the sender no good any ideas were is the fan module located at

and whats it look like

Check the fan bearings/bushings. Increased vibration could cause a speed decrease if the bearings are failing.

You can also check the fans amp draw with a Multi-meter. It should be constant over the RPM range. A higher amp draw at higher rpm's could also indicate a failing fan motor/bearings.