My lights come on when the key is half turned but when i turn it all the way nothing it a 1981 suzuki 400cc kickstart

A few questions so I can help. Is this a Suzuki motorbike or a car? What EXACTLY does it do when you turn the key? How did you 'check for electric'? A vehicle battery should have between 12.6volts to 13.2 volts.
When you turn a starter motor over it needs a large amount of volts to power it, anything under 10 volts and it will struggle. Even a fully charged battery can struggle to turn a starter motor if it is old or faulty.
Try this. First look at the battery and check the terminals are clean and tight. Sometimes it can be as easy as that. Turn the key and look and listen carefully. Try to start the engine. Do you get absolutely nothing and no dash lights? Do you get dash lights which go off when you start the bike but you only get a quiet 'Click'? Do you get dash lights which go off and then a louder 'Clunk'? Does the engine turn over but it's very slow and lazy?
Absolutely nothing suggests a dead or totally flat battery and a lazy, slow starter is a low charge in the battery. A Quiet click could be the Starter Relay and a louder 'Clunk' could be the starter solenoid or the starter itself.
Use the comment button below with more information and i'll try to help more.

i presume the bike must be in gear to move the front sprocket. does the piston move if try and bump it in gear..if not.the piston has somehow seperated from the krank, need a visual inspection, head needs to come of, possible more. if it does then need to look at kickstart mechanism

Rock the bike gently forward and back while shifting into fifth gear. Now push the bike forward while sitting on it and see if the rear tire turning will turn the motor. If not, your motor is stuck. If it turns, you have a kickstarter issue.
Many people never learned to depress the kickstarter down until you feel it engage before kicking it through. Kicking from the top slams the gear teeth together and causes damage. You may need to pull of the engine cover to determine if there’s damage.

Hi, does this bike backfire at all? Noticable as the kickstart hits you hard as you try to start the bike, these bikes used to suffer with cdi ignition failure, eventualy breaking the kickstart ideler gear inside the gearbox which in turn the oil pump drive was also fitted to this,

I appreciate that this is only a similar problem but my wife had a similar problem with her old vaxhaul corsa, we got the big guy across the road to help because big guys are usually good with this sort of thing lol, ok he had a great car lots of tools and was always inside his cars engine. He came across half hour later with jump leads and I yelled stop because not just sparks but the cable covers melted and I found it to be a little off. after that we had nothing, no ignition, no lights just nothing and a car mechanic came looked in the engine but couldnt see anything we explained about the battery and on testing it he found that the battery itself first drained as suspected and then we broke it by overloading it somehow in the end a new battery sorted the problem which cost £50 but in the long run we thought it a good price. the battery lasted us another 4 years until the car had had enough and went in for scrap. hope you can take something from that and you can sort your bike :)

Just remove the kick lever then remove the right side cover. This will allow access to the kick start mechanism. Please rate my answer.

Lightly seat both the air screw and the throttle screw. Now turn each of them one and one half turns outward. This is the factory setting.

try repairmanualclub.com they have several manuals for free download they may have yours i found one there before for a 1981 gs550

Your best bet is to go to a Suzuki shop and get one there. That way you know for sure you have the right battery and that it will fit your bike.

The bit that ingages the kick start is half way along the rear hand break cable.
you can push it with your hand and kick it over.
also try re tensioning you brake cable
this can be done at two pionts along the cable at the end or on the balance bar (10mm spanner required)
This needs to be adjusted as the pads wear down.