Electrical help please

[JB373]

Hello all, I have been working on a 71' CB750 K1 as my first project. I am relatively comfortable finding my way around the mechanical stuff but when it come to electrics I struggle so would really appreciate any help anyone can give - so here's my problem.
I last rode the bike about 6 months ago as I've been working on it over the winter, I have come to start it and there was nothing. I have had the battery on trickle charge over the winter so thought it would be ok. The headlight and brake lights came on but it wouldn't turn over the reading from the battery read about 12.7v but when I turned the ignition on it dropped to 8.6v so thought it may be the battery so I have just replaced it with a new one. It still won't turn over and now only the neutral light will come on the headlights, brake lights horn etc now do not have power and I have tried hooking it up via cable to a car battery to see if that helps - it doesn't still on the neutral light. I read in another thread about bridging the solenoid terminals to see if that works - i got sparks and it turned over - thats as far as i have got - does this make sense to anyone…please?

[JB373]

Thanks for your help Oddjob - appreciated.
I've been out to the shed and inspected - as daft as it sounds I can't find any fuses coming of the solenoid. I have tried taking a picture but it hasn't come out great in the limited light. I'll try again tomorrow in daylight.
Does that the fact that the lights don't work either (other than the neutral warning light) help with diagnosing the fault?

[JB373]

Thanks for all you helpful suggestions Oddjob, I have been in the shed all day today working through your ideas. I cleaned out switch which wasn't too bad and I have cleaned up the fuse (the fuse didn't look like I expected it to - a big cylindrical thing) so now all the lights work but it still won't start - there's nothing. There is no clicking coming from the solenoid but when I bridge it the starter motor turns over. I don't know where to go from here - any other suggestions - how can I test to see if the solenoid is knackered?
Any suggestion appreciated as always

[mickwinf]

could be the handlebar switch or wiring, does it kickstart? To check the solenoid connect the two thin wires to + and - of the battery with a couple of wires, it should click as the windings are energised.

[JB373]

Thanks all for the help - i have managed to get it going, i disconnected everything and reconnected then cleaned and reinstated - i think it was the solenoid that wasn't grounded. Anyway made todays ride all the more enjoyable…...