I have Kawasaki zxr 636 it will not start when cold it trys to fire but won't 20 mins with jump lead it starts and is ok leave it a month it will not go

its an alternator not magneto, there should be 3 wires white or yellow, going to the reg\rectifier, multi meter across any pair(unplugged) should show 50-80 volts at 2000rpm non of these should short to earth, multi meter across battery should show up to 14v at 2-3000rpm.with everything plugged back in
if alternator checks out, and no voltage more than 12 at battery , replace regulator,,

all assuming the battery wasn't fried when it ran out of acid

my guess is new stator\alternator required

My guess would be faulty spark plug lead.

Prob miles off here but my zx7r did this after being sat 20 months. Turned out it simply had exhaust gaskets totally inoperable. The block where the pipes come out, therefore was in fact sucking air in as the hot fumes were spitting out, mixing up and creating a mini explosion. Check pipes are all sealed nicely tightly. Everything else you did sounds right. What about lifting tank off - airbox off (check that) and look at carbs? clean? Sounds daft this but is it sat with 2 year old petrol in the tank too? It's as if the mixture is going in, plug is igniting but then like its no compression? Mine 'was' simply exhaust gaskets. Think they would do the same if you totally stripped the whole exhaust off and tried starting with a couple of dirty great holes in your bore. Will it not even start with jump leads to a large car battery? Did mine to our landrover and forced it to start - endless charge from running landrover. Take a plug out, connected to your HT lead, turn it over but touching / earthing plug onto part of your metal frame / casing. Should see the actual spark, if not its your coil / ht leads??? Not an expert just had Kwakker long time lol. Love hate relationship.

you need to see if you have a spark at your plugs...this is your first step

clean your carburetor and gas tank and change all sparkplugs

Have you drained the old petrol from the carbs? Do this by way of the drain screw at the bottom of each carb.
As long as there is a spark it should now fire-up

Good Luck
Hope this helps.
(If it does then please mark this as 'useful')
Ride Safe
Bike-Doc

Hi and welcome to FixYa,

On your post "...does not fire..." initial checks would be for:

• consistent IGN + 12 on the red wire going to all the ignition coils even when cranking;
• pulsating voltage on the other wire of each ignition coil coming from the ECU when cranking.

Incidentally, if the bike has been sitting for 2 months, you may want to check quality of fuel and/or replace it. Further checks maybe required on the fuel delivery system. Try of a quick fix would be adding / spraying injector cleaner.

Good luck and thank you for asking FixYa.

Did you put the correct leads on the correct cylinders?

hi mate i did have a zxr 400 l9 : and i didhav same problem its one of 2 things eather coil triggering pick up on flywheel or coil packs breaking down it took me agies to fin it good luck and let me no if you solv problem chears