Kawasaki GPZ 750E problems

[Scotauto]

Just bought a GPZ 750 and am having a couple of problems with it.
1.The airfilter housing fills up with petrol as soon s I fill the tank.
2. When I put it in gear it stalls instantly. I have managed to keep it running in gear a couple of times but both times the rev counter has not worked (the rev counter works when it stalls!) I would appreciatte any guru mechanics out there who have any suggestions. Is the wiring on a GPZ 750 the same as a ZX750?

Jason

[StarGate]

Your carbs most likely need a rebuild but at minimum you need to clean/replace the float valves. If you have a vacuum petcock you need to rebuild that as well.

[StarGate]

You also need to read this.
http://www.kawasakimotorcycle.org/fo...st-please.html

[Scotauto]

I get the point but I don't know any more about the bike other than it is a GPZ 750 from 1983. I have owned the bike 1 day... and have never owned one before. I am however a car mechanic and understand how engines work but before I strip things apart I thought there could be some words of wisdom to be found here on the forum. What about the putting it in gear/stalling problem. Any ideas?

[antiq]

It's flooding! A thorough carburetor cleaning is the minimum fix available to you. Still a good idea to replace the float valves.

[Bren]

I agree with Stargate. You say you have only had it 1 day though.

If the previous owner left it standing for a while without draining the petrol out of the float bowls the float valves gum up, but that normally results in flooding. The symptoms of which are a choking and cutting out engine and sometimes fuel in the oil.

To check if flooding is the problem turn the fuel tap on and start the bike then after 15 seconds turn it off for a minute then on for 15 seconds and just keep repeating. You might have to adjust the on/off frequency times a bit but if the bike can run indefinitely without cutitng out doing that then you know it's flooding and you need to sort the float valves.

Because it's filling up your airbox firstly I'd check that that the previous owner hasn't mixed up the smaller diameter pipes on the carbs. 3 are breathers and 1 is the vacuum feed for the fuel tap (petcock). If you pull the petrol tank, turn it 180 degrees and sit it on some steps or w.h.y. next to the bike it can still run and you can get to the pipes to disconnect them 1 at a time and it's easy enough to tell which one is sucking air when the engine is running.

Also inside the fuel tap there is a small diaphragm which can perish allowing petrol to get sucked into the air system. Normally there are 2 small screws on the tap which allow you to strip it and check. Make sure you get the gasket with the diaphragm if it is that.

[StarGate]

Originally Posted by Scotauto

I get the point but I don't know any more about the bike other than it is a GPZ 750 from 1983. I have owned the bike 1 day... and have never owned one before. I am however a car mechanic and understand how engines work

Yes you did and now we know the year model and a little about your abilities and that we are going to be working from scratch basically. You being a mechanic, I'm sure you understand what that little bit of info can mean when trying to help fix a problem over the internet.

[Scotauto]

Thanks for the info. I suspected the carb floats but nice to get confirmation. Anyone got ideas about the stalling. It is directly related to when I put it in gear. Electrical I suspect but i haven't had time to check if there are some sensors or other electrical devices connected to the gear shift.

[StarGate]

Not sure if that model has a kickstand switch but you could check on that. If it dies as soon as you start to let the clutch out.

[Scotauto]

there is no kickstand. It is when I pull in the clutch, put it in 1st gear then it stop instantly...

[Scotauto]

sorry of course there is a kickstand..... i read that post a bit too quick!!

[Bren]

Is it a clean simple cut out when you put it in first or a stall? Is the bike upright or still on the side stand?

I don't know if that model had the tilt switch as well or just the side stand down cut-out. If it has the tilt switch then as well as the wires coming from a switch on the side stand mounting bracket there is an additional switch with 2 wires on the underside or back of the clutch lever assembly, it is easy enough to check the switch operation with a multi-meter or short the wires together temporarily to eliminate a switch problem.

It is more usual to get a problem with the switch on the side stand though as they can get covered in chain grease which then solidifies over time. Try tracing the 2 wires from the side-stand coming up (normally along the frame tube behind the front edge of) the left hand side panel to where they meet the main wiring harness at bullet connectors and check that switches operation by holding the bike upright and putting the side stand up and down while a multi-meter is connected. Again you can link the wiring harness bullets together temporarily to eliminate any side-stand switch problems.

[Scotauto]

It's clean and simple not a normal stall

[Bren]

Sounds like the side stand switch staying open circuit then, if it is the engine normally runs until you put it in gear which seems to be what you're saying the problem is?

It should be easy enough to find on the side stand bracket unless it's caked in a large blob of deposited chain grease. Although I did once buy a ZXR750 dirt cheap as a non runner and the guy just hadn't realised the side stand switch had been wiped out on a kerb when the bike had been knocked off the stand by a car.

I'm not sure about how many differences there are in the wiring, the early ZXs were almost identical to the GPXs. Is your GPZ750 the 6 speed sleeved down 900 or an earlier air cooled version?

I have wiring diagrams for the ZXs I could email you and have a mate who is into air cooled GPz 11s who might have a diagram for the earlier 750s but couldn't help if yours is the last of the GPZs.

[ronin1959]

Originally Posted by Scotauto

It's clean and simple not a normal stall

I guess we should ask "is the sidestand still down when you put it in gear?"

The GPZ's have a safety cutout system that prevents the bike taking off with the sidestand down - it will simply stall when you try to put it in gear.

If the sidestand is up, then either your sidestand switch is faulty or the clutch switch is faulty. GPZ's are renowned for sidestand switches going open circuit.

Trace the wiring from the switch to the harness connector and test continuity when the stand is down. If same continuity when stand is up, then switch is faulty.

HTH, Ronin

[Scotauto]

Sorry It's been a while getting back. Anyway just an update for everyone who has helped out. The kickstand switch is fixed and has solved the putting in gear/cutting out problem. The carbs will be rebuilt soon, as well as the tank valve and I am 99% sure this will stop the overflowing problem. Some new spark plugs; filter and an oil change for good measure and hopefully the wind will soon be in my hair!!
My alternator lamp is blinking all the time though. The battery is recieving a charge and holding it.

[StarGate]

Might be a good idea to test/verify the charging system output.

[dr_aplet]

super strange i have just bought the same model bike 1983 750 gpz and the carbs are flooding, no high end rev almost like a missing vacuum line. stalls when letting out the clutch. i have been following this thread. great ideas for me to follow. i do see what looks like a second port on the Petcock, vacuum i assume. but where does it go to? is it from the carbs? or another port that is open possibly. i am waiting to hear about a manual from the kawi dealership locally. they told we that most parts are discontinued. on the kickstand switch, i see a bracket that would probably attach a switch but its gone. where would that plug in and can i get a new one? i checked the clutch and found that there were three wires coming out of it. when checking continuity the outer pins had continuity but the middle pin had none. i checked with the clutch depressed and released. no change. is this a magnetic switch? i saw no mechanism perhaps on the inside. my "warning" light is constantly blinking i was told that is was because the battery had not charged. i wasn't sure that was the cause but i didn't argue. Hey Scotauto are you from Califiornia? it seems like i bought your bike. LOL well guy i hope i can get some help on this. i was looking for a commuter bike fairly cheap ($700)and no one called me back. can we make the beast go?
P.S. i am a moderate mechanic with exoperiance in cars/trucks and small engines. but assume nothing and i will make no pretense. i have swallowed my pride a long time ago.

[StarGate]

There should be 2 fittings on the petcock. One large one small. The large one is for the fuel line and should run down to the middle of the carbs to the T in the fuel rail. The small one should have a vacuum line that most often runs off the #2 carb but can run from any vacuum port. The side stand switch may have been removed and bypassed but you need to verify that. The clutch switch should have a little plunger type button that is pressed by the leaver when it's released. Pull the clutch in and look between the cable and handlebar.

[dr_aplet]

thanks i have started making headway in this project. i added a vacuum line from #2 carb to the fuel petcock. then i took some starting fluid while the bike is running and sprayed it all around and found major vacuum leaks. i ordered 4 carb kits to rebuild the carbs. but i am concerned about the Plastic balance tubes connecting the carbs today i found out that they are $45 each. and the diaphrams are $177 ouch. the Manual is $30 on its way. well i'm gonna start with the kits and see where its takes me.

If you all have a parts person that is reasonable could i have that nugget of information.