Topic: starting problems with my 1983 Kawasaki GPZ 750

[torrinh]

Hey guys I need a little help with this one.
My used-to-be-reliable commuter bike, the 1983  Kawasaki GPZ 750, developed starting problems last week and I can't figure it out. It used to start with almost no problem in the morning, even when it was near freezing out. (I'm going to school in Northern California so it never gets below 30 degrees) When I couldn't start it i would take my 1978 Honda CB750K to work instead, which starts first kick, every time! I thought the Honda was the unreliable bike. Usually I don't take the Honda because I have to park in a sketchy area full of transients and bums who might tip over my shiny ride. The Kawasaki is beat to hell but runs awesome, when it starts, so I take that because it looks like a piece.

The facts: it started fine in the morning until last week or so.
Once it warms up into the 50s or so the bike starts, albeit with some hesitation.
It's an electric start, so no kicking this beast.
One morning I tried starting it with some starting fluid. She backfired, scared the hell out of me and nearly blew my eardrum out. She didn't start that morning. Started later that day after it warmed up outside.
Thinking it's an ignition issue I pulled a plug and grounded it to the head. Nice spark.
I pulled the carbs and took off the float bowls. Clean, clean, clean. I didn't check the jets but I have a feeling they're fine.
What I noticed is that when it does start it's immediately after I've released the starter button. So, thinking that the battery is weak, and maybe old (it is) I bought a new battery today and am charging it right now.

If this doesn't work I'm at a loss. It's getting fuel, the plugs are sparking. Nothing's changed with bike as far as I can tell. WHAT'S GOING ON ? I can't figure this out. Please help me if you can. I'll let you know tomorrow if the new battery starts her. Short of that, I'm going to pull the carbs again and clean the jets. Thanks guys.
-Torrin

[crazypj]

How old is the battery?
 What your describing does sound like it reached the end of its life.
 When motor is turning the voltage can drop below 9.5~10V which wont be high enough for reliable ignition.
 When you release starter button the voltage instantly rises and flywheel momentum keeps crank turning enough to start it (sometimes)
If you have a multi-meter, you can check cranking voltage,it shouldn't drop below 10 volts  I've seen them go down as low as 8v and still turn over
PJ

[torrinh]

The battery came with the bike when I bought it back in November 2007. The PO hadn't maintained it well and it was bone dry. I refilled it at my school's science lab with distilled water, then my roommate and I jumped the bike with his car and I rode it for two hours to get the charge up. Until last week, it hadn't given me any trouble, even on colder mornings. This model bike actually came with a voltmeter built into the speedo housing. I checked it after it wouldn't start the other morning and it was just below 12v. After cranking it a few more times it was down to like 8 or 9v. When I pulled a plug to check the spark, it seemed like a healthy spark, but my theory is that with less compression for the starter to fight, the battery could put more oomph to the ignition, and therefore give me a healthy spark.

I'm installing the new, charged battery this morning to see what happens. If it's not that, I'm at a loss. Fuel, ignition are fine.

[Soos]

If the 750 GPZ carbs are anything like the GPZ600 carbs, clean the starting circuit....
??

I had a HARD time starting when I first ran them on my cb650.
started fine over 60 degrees, under 40, it was a PITA.

After a Second cleaning of the starting (choke) circuit, started (with a charged battery) in as low as -2 F. weather.


l8r

[dusterdude]

choke issue?

[torrinh]

Maybe it's the choke. Now that I'm back from class, I'm about to put the new battery in.

If it's not that I'm going to check the starting circuit.

Soos, did the GPZ600 have mikuni cs carbs?

[torrinh]

SUCCESS!!!

I put the new battery in, barely touched the starter and VROOOMM!!!! Like a champ. The real test will be tomarrow morning when it's cold. But I'm happy for now.

Thanks for the help everyone!

[Soos]

Maybe it's the choke. Now that I'm back from class, I'm about to put the new battery in.

If it's not that I'm going to check the starting circuit.

Soos, did the GPZ600 have mikuni cs carbs?

Lemme go check....
The bike was a ninja600 ('84), the had GPZ600 cast into the covers. It has a Keihin CVK 32mm venturi set of carbs. 
Thought they might share similar carbs as well.

Glad it was the battery!
cleaning carbs sucks,  but is worth it if you gotta.

l8r

[HavocTurbo]

Humor me and take a picture of your start button assembly....

If I were you... and If I'm correct... clean your starter button terminals. That dead battery might have burned them a little.

Depending on your assembly, Kawasaki had problems (well in IL anyway) with a certain design. Humidity would get in the starter button and while there was a good charge.. no problems.

When your battery was close to the end of life it would scorch the terminals a little. There's a spring in there so be careful.

Not saying that was your problem.... but it can lead to one later. Especially now that your battery was junk.

[crazypj]

Its not the starter button that burns, its the contactors inside starter relay (the buzzing/clicking when battery is low)
PJ

[HavocTurbo]

Its not the starter button that burns, its the contactors inside starter relay (the buzzing/clicking when battery is low)
PJ

In the last 3 years I have replaced/repaired more starter buttons than I can count.  The surface area is almost half what it is in the starter relay. Press that button repeatedly long enough, and it WILL burn with a low battery.

Yes the starter relays can go bad.... but that wasn't what I was talking about.... notice how I hadn't mentioned noises?

[crazypj]

The starter button carries 12~14 volts at about 0.25 amps or less. (unlike contact points which get up to about 180~300 peak volts, that can/does ionize the air between contacts)
Its normally spray lube , contact cleaner, oil from throttle housing that burns onto/into contacts.
Contact 'burn' when you let go of starter button not when you press it.
 Clean contacts don't burn so there is something else going on if your replacing/repairing a lot of starter buttons.
PJ

[HavocTurbo]

Nevermind.... I'm just a child.

You are right, oh master of everything motorcycle.

What could I possibly be thinking by making a suggestion.

[maneet]

Hi , Verry new here . I need some urgent help with my Gpz 600rA 1987. It never starts in the mornings without a good push. I have brand new battery. Enough fuel. One i get her warm enough though , she will start at the first go. Normally seems to happen in the mornings after the bikes been lying for 8-9 hours. However i dont have any problems when i ride her at night.
I live in India where it isnt really really cold. I live in a place where it has never snowed , so dont really know where to look.

Can anyody please help.

Maneet

[crazypj]

Hi , Very new here . I need some urgent help with my Gpz 600rA 1987. It never starts in the mornings without a good push. I have brand new battery. Enough fuel. One i get her warm enough though , she will start at the first go. Normally seems to happen in the mornings after the bikes been lying for 8-9 hours. However I don't have any problems when i ride her at night.
I live in India where it isn't really really cold. I live in a place where it has never snowed , so dont really know where to look.

Can anybody please help.

Maneet

You need a valve adjustment-URGENT.
 Its a shim under bucket motor and you have classic symptoms of tight valves.
 The cylinder head expands when it gets hot and gives you some clearance but when its cold the valves are barely touching valve seats.
If you do (or have done) compression and leak down tests, it may show which (or all) cylinders are 'off'
 I wouldn't worry about engine damage at present but if you continue to ride without a proper service it will cause damage. (usually exhaust valves burn out)
I've found its a good idea to set valves about 0.001"~0.002" looser than spec when you get them done, they will bed in to correct clearance within 100miles or so
PJ

[HavocTurbo]

DITTO!!!!

[maneet]

Hi Guys, Thanks a lot for the suggestion. Its worked wonders. The bike starts first shot even about being cold for 48 hours. However 1 question. The bike sounds really noisy . specially tappet noise since i did the valve clearence adjustment. have kept it as per the manual ie .14 mm for the inlet and .18 for the exhaust. Is it supposed to sound so noisy.

2: i have another problem with the bike. The colling system seems to be acting funny. the collant keeps overflowing and empties out the radiator. It also dosent pull in any coolant from the reservoir. The radiator is actually throwing out hot steam into the reservoir. It sounds like the water is boiling in the reservoir. any suggestions.Checked the water pump. there seems to some play in the fan but is pushing and circulating the coolant well enough.

Regards,

Maneet 

[crazypj]

0.14mm is  about 0.005", 0.18 is about 0.008"~0.009" you didn't set a 0.014" and 0.018" did you?
 Tappets probably sound louder because you have some clearance.
 Sounds like you may have a vapor lock in system somewhere, re-fill and leave radiator cap off to get all air out of system.
 The header tank only returns fluid to radiator when engine cools down, it doesn't circulate through there
Are you using coolant designed for alloy engines? plain water doesn't lubricate water pump and thermostat wont work right either ( don't know why, it just happens?)
PJ

[HavocTurbo]

for some reason, the factory techs all say that alloy specific coolant has some sort of chemical in it that lubricates. water apparently will oxidate the parts faster under heat and pressure.

Still not sure about it but..... oh well. fixing and maintaining isn't supposed to be cheap I guess.

[crazypj]

Is it the one with the 'U' shaped water pipe going into head through cam cover? ( needs to be drained and removed to check/adjust valves?)
 It could be a leaking 'O' ring. I thought the 1983 was still aircooled?
PJ

[HavocTurbo]

as far as I know it is... I know my 85 turbo is air cooled.

I thought the 900 was the "first" gpz based bike that was water cooled?

then again it might be some distant model.

[HavocTurbo]

Did some checking, the first 750 water cooled bike was the 87 ZX-7.

At least from what I could find anyway.

[Soos]

I know the '84 gpz600 bike(ninja, but all the motor covers said GPZ600) I had was water cooled.


l8r

[crazypj]

I knew the 600 was water (worked on a bunch at Suzuki dealers) but I thought the 750 was still air in 83?
PJ