Oh look.  It's that B33 again.  I've now slackened the drive belt, this has more or less solved the transmission problem.  I did a fair few miles on Saturday, and had the exhaust pushrod jump again.  A bit more running-in is needed.  On Sunday I did just under 300 miles with no problems, and the bike returning an amazing 90 miles per gallon.  On the down side, either the oil line unions are leaking, or the tank has split.  I dare say I'll find out soon enough.