hi all, bike has been  off road 1 year. was running fine, put new battery on, no sign of life from lights, horn, nothing. checked main fuse power getting to ignition switch. I had to remove engine to repair exhaust studs that's all?

I'd hafta check the battery, and as stated, grounds..

Check connections under the tank.

ALL OK APART FROM ground - I attached a separate ground with clips from batter to engine and hey presto - but I can`t see whats missing - the wire from near oil glass to starter ok, cable from battery negative goes ti a round switchy thing along with power cable from positive. have I simply lost the main earth lead somewhere in transit...…..
thanks to all - ps I meant to take pictures but failed to do so

yikes! First) the power from the battery positive(red) runs to one side of the  starter solenoid( the round switchy thing mounted to the bracket on the rear fender under the seat) from the other side of the solenoid the cable runs to the threaded stud on the top of  starter motor .( this is the positive leg of the circuit).  Next)  the negative leg is the ground wire(black) connected to the battery and runs  from the left side to the right side of the bike to the bolt near the oil site glass,(do not run the ground from the neg . battery post to anywhere but a casing bolt) the rest of the circuit is the motor case itself, which acts as the rest of the ground  to/for the starter motor.
    ALWAYS connect the neg. lead to the battery last !!!   (if you connect it first, and touch the pos. to the case ,frame fenders etc . which are then grounded the  battery could short circuit and explode) Never touch the pos. and neg. leads together !     you should wear safety glasses to protect your eyes from sparks /acid.