Motorcycle Repair: cbx 1000 starter clutch, vernier caliper, piston skirt

Question
hi jan ,i am working on a cbx 1000 78, which belongs to a friend who has had the bike in storage for many years ,not started or moved ,i have spent many months rebuilding shocks brakes forks and worst of all the carbies which were in a shocking contition,i finally got the bike running and took it for a ride and it went fine,i went to start it to return it to the owner but while starting the bike there was a sort of kick back or resistance and when running there is a load rattle,im told this could be starter clutch,i have checked the cam chain tensioners and they look ok ,hope you can help
thanks brian

Answer
Well Brian I was rather hoping I could give you an easier answer.  As you know changing the starter clutch is a total engine strip, so you may already be prepared for that.  I do not believe it is the starter clutch.  I believe when you stopped the engine after taking the bike for a ride, you left the fuel on.  When you returned, one of the cylinders had filled with fuel and when you started it, the kick you felt was one of the connecting rod bending...  The rattle is the bottom of the piston skirt touching the crankshaft.  Easiest way to check is to remove 1 and 6 spark plugs, and measure the distance from the head to the piston with a vernier caliper.  You will probably find a difference of about 2 mm between the two piston heights!  If it isn't 1 or 6, repeat for 2 and 5 and lastly 3 and 4.  Usually it's #1.
Engine strip and connecting rod replacement I'm afraid.  This could have been prevented by turning the engine over with the kill switch OFF whenever the fuel has been accidentally left on on a CBX.  The starter motor is not powerful enough to bend the conrods, but the engine firing is.  Let me know,  Jan