tiny tach
On my 600 I used a 'tiny tach' that was spec'd for 2 strokes. Comes with its own internal battery, and you wrap a wire around one of the spark leads. It also has an engine time which is interesting to see how few hours these engines actually get onthem. From what I remeber it was about $25. Problem is it is super small but it was good enough to know that during long pulls in powder, wide open I was at 8100 RPM. When riding on the trails though, you couldn't see then numbers changing so not much use there but good enough for wide open smooth uphill climbs to ensure the clutching clickers are set right...