My first bike was a H reg TZR125.  I have to say there was a real nack to starting it with the kick start and the throttle.  I could always start it but every one else used to struggle.  When I sold it I spent a few minutes showing the new owner how to do it,  it took him a few attempts and then he got the hang of it.  I am not saying thats it but it doesnt help.  It could be an air leak on a bike that old as the rubbers are bound to be perished in places.
