Kz750 e

Hi, I'm new to this forum and I was hoping I could get some help from all you enthusiasts.

I have recently rebuilt a 1980 KZ750 E model and I can't seem to get it started. When I push the starter it just turns over but won't fire. If I give it full throttle while starting it it kind of ticks over but sounds lumpy. After about 1 minute it pops and dies, sometimes back fires as well. If I take the throttle off before it pops it just dies. Does anyone have any ideas what it could be please.

Also with the ignition coils, does anyone know which electrical wires go where on the coils. For example
Sitting on the bike, the left hand coil (1&4) has a black and red wire, which goes on the top terminal and which on the bottom. Same with the right coil (2&3) green and red wires. If these were wrong would it not produce a spark at all or would it spark but in the wrong sequence?

Please help
Thanks Hips

Regarding the coils: normally 1 & 4 would be on the right hand side, but the black and red wires are correct. Somebody has just switched the sides for both coils but still wired them up correctly.
I would check that the cams are in the correct position (couldn't hurt to check valve clearance when the cover is off). After that check for spark and then check the timing. Someone else should chime in here cause I'm sure there's something I'm forgetting to mention before you start looking at the carbs...

If you turn the gas off and shoot some starting fluid in does it run at all? That might be a good first step since it should verify mechanical timing and ignition timing.

Hi Callum , thanks for the reply. Yes your correct, probably my mistake not how they are on the bike.
I replaced the head gasket during the rebuild and followed all the manual instructions of putting the cams and chain back in so I am pretty confident that's ok. I did also check valve clearances and they were all within the specs.

Did you break down the carbs and clean them properly?

Hi Matt. Thanks for the reply.
I have squirted some easy start in the carbs and it didn't even make it fire. Nothing happened.

Hi nessism.
I did clean carbs thoroughly last year. They have been in my garage in a box since. Didn't think I would need to give them another clean.

calum wrote: Regarding the coils: normally 1 & 4 would be on the right hand side, but the black and red wires are correct. Somebody has just switched the sides for both coils but still wired them up correctly.
I would check that the cams are in the correct position (couldn't hurt to check valve clearance when the cover is off). After that check for spark and then check the timing. Someone else should chime in here cause I'm sure there's something I'm forgetting to mention before you start looking at the carbs...

Just an update on the cam situation.
I've taken the cam cover off to check the Mark's are correct at 'T' mark and it seems that I must off accidentally moved the timing points thing when removing the socket spanner so the 'Z7EX' mark on the exhaust cam sprocket is about 10mm above the gasket surface and the inlet cam sprocket 'IN' is 10mm below so as I say I must of accidentally knock it out. Probably needs to be moved 1 tooth along.

So my question is, with it being 10mm out would that stop it from starting??

Any help would be appreciated please.
Oh and just so we are all on the same page my bike is the UK Z750-E1 model.
Thank you

One tooth out of cam Timing could give you some bent valves if you start the engine.

Cylinder #4 Cam notches position @ piston #1&4 TDC position.

Hips wrote: So my question is, with it being 10mm out would that stop it from starting??

The symptoms you described would be what I would expect if the timing was out. Your valves would have been opening and closing late which means the inlet valve is open for too long on the compression stroke so you won't be getting nearly enough compression.

Also, what scirocco said - although I'm not sure the clearance on the 750 is that tight. You'll want to do a compression test when you've got it sorted just to make sure nothings bent.