Well, just got all the parts replaced that needed replced
(sprokets+chain) and notice that engine still taps like it did before.
All our local 'experts' say it's the tappits that need some adjusting so
I am soon to attempt that.  I would like any advice anyone had.  I do
not have a shop manual but have read about the procedure in Chiltons and
in a few other places.  Is there anything I need to be particularaly
carful of?  Any problems anyone else has encountered?

I ride a 1981 Yamaha Exciter 250cc (stop laughing, it's tiny, but it's
shiny)
