A chain oiler. Teensy gauges too...

[bikerjimbob]

I've used  scottoilers on most of my motorcycles since i acquired my fj in 91 with one fitted.
The fj is still on the original chain at 30+ years old and runs nicely with no tight spots.
Whats not to like? They are very simple devices....

I completely agree with Urx I have used Scottoilers on all sorts of bikes for many years never had a problem one set right and extended chain life is a great bonus.