I also ride a '74 R90/6 for 12 years, and I read that the consensus about kick-start is don't do it.  The reason is that the gears mesh in such a way that bits of very hard gear-tooth material is chopped loose and floats around inside your gearbox causing damage.  I removed the lever as soon as I heard this.  I use a Shorai battery and have never yet had a no-start incident so I don't miss the kick-start feature.  I am happy to see an old Airhead being resurrected!