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Discussion Starter #1
Hi all,

I'm new here, I just picked up a '84 GPZ 750. The bike had been running but was stored for a couple of months and, now, won't idle.

I've gotten it goin about five times but only for about ten seconds or so. Never gave it throttle as its cold here in the DC area and I thought the choke being already out it would be too much—but maybe not. I've tried starting the bike with the fuel valve set to PRIME, ON and RESERVE to see if that helped. Prime was the best, is one would expect.

The sparks are sparking nice 'n' blue and their wetness indicates that gas is indeed getting to the cylinders. I also checked the air filter which appears to be new and very clean (note: while doing this I noticed a bit of oil in the airbox, I'm assuming this is from the gearbox drainage which lets out into the airbox. Could it be anything else?)

So, sparks seem good (they are new—as are the cables), gas is getting to the cylinders, the air filter is clean and the bike has run for brief intervals. Then what could be wrong/how could I get 'er started? I'm guessing this is likely a carburetor issue of some sort (I'm not very experienced working on bikes but am capable and motivated). Would spraying some starting fluid into the airbox help? I feel as though the bike just needs to be run for a while maybe with some carb cleaner to get things cleared and moving again, I've been told, or rather reassured, that the bike was running smoothly up until a couple months ago when it was stored. Any suggestions? I'm at a loss. May an oil change to get thick old oil out.

Also, the battery is new and hooked up to a tender.

Thanks for any input! I wanna ride!

Francis
 

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depending on how long the bike was stored for the fuel may have gone bad( I doubt it if only for a few months). don't spray starting fluid in the airbox but try in the cylinders via spark plug holes.
 

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So you have air, gas, spark. All is good but are they good? Sounds like you have good spark (blue arc). Air sounds good since you checked filter and it was clean. Try to change gas since we don't know how good/fresh that is.
These bikes are cold blooded and depending on where you are the weather may be cold. This does not help to atomize gas/air to burn. It may take several attempts with short runs until it warms up and you have good gas flowing.
I have auxulary gas bottle to enusre fresh gas and I run for long time before going to gas tank, also filled with fresh gas.
 

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Discussion Starter #4
Hey, Thanks for the input.

The gas in the tank is fresh, I put it in a week ago. When I picked up the bike the fuel got detached from the tank and what was in there drained completely. There wasn't much in there. What I'm thinking is that the carbs have old fuel in them that has begun to gel. I'm not sure how likely this is given that the bike was only sitting for a month or two.

Also, it is cold here in the DC area, and that is certainly somewhat to blame for these starting problems. Its gonna get up to 60 tomorrow so I'm hoping that might help. I've used a heater-fan in my garage to heat the engine up and that seemed to help some. Hopefully with warm air things will get moving.

Another detail I noticed is that the tank seems to have been lined with a sealant or something to that effect. There is a tan/pinkish coating that is chipping a tad in the short tube below the gas cap. However, as the the sparks are wet I'm guessing there is no blockage in the fuel system.

Don't know where to go from here! Maybe rebuild the carbs—which is always a good idea in an old bike—but I've never endeavored that before and don't have excessive time at the moment. I'm guessing I need to check vacuum lines and fuel lines alike.. I'm waiting to really break the bike down until I try to start it in warmer weather.
 

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Discussion Starter #5
Another thing, the neutral light does not come on when the bike is on the center stand or in riding position. It does, however, come on when on the side stand. I'm guessing this is just due to a dirty connector or something. It doesn't keep the bike from turning over but I do have to hold the clutch in to start the bike when the light does not come on.
 

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Discussion Starter #6
Just got 'er to idle for about 15 or more seconds, seems like the problem might be fuel delivery. was in the 2000's for the first 10 seconds then started slowly dropping before it cut out. Seemed like it lost fuel, the prime setting not providing enough... I'll guess I'll have to check the fuel system, lines, filter, vacuum hoses.. and I don't know what else really. I still think its just gummed up carbs that I might be able to get clear in the warmer air tomorrow. We'll see.
 

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check the ignition switch connector with a multimeter. it is possible the contacts inside the switch are dirty or corroded. the back of the switch should pop off with minimal effort if you can get to it.
 

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Discussion Starter #9
Hi All,

The bike is running now, but it surges and then Idles low and seems to be a bit rich at idle and lean at high rpms. A bit of smoke in the exhaust but nothing substantial. The high revving when choked seems to have busted the head gasket...

...so I've decided to do a top end engine and carb overhaul in early march—when I have two full weeks of time to dig into things. On the head I'll be lapping the valves, most likely replacing the oil seals and replacing the cam cover and cylinder head gaskets as both are leaking. I won't have time break into the engine past the head though I would love to. I think I'll wait and do that when I'm read for the big bore kit. Hopefully I find no nasty surprises in the in the cylinders.

Ill be installing fresh boots on both sides of the carbs. I was planning on ordering the carb rebuild kits from Z1enterprises and do a ground up rebuild (excluding the floats (which are in very good shape) and, hopefully, diaphragms which I have yet to inspect.). I'm thinking disassemble, strip paint—which is already leaving of its own accord—and then chem dip, rinse, check all passage and clean with spray where needed. Then rebuild from the ground up. Maybe I don;t need to go this far.

I'm also gonna rebuild the petcock which I think as it spews gas in every setting alike when the fuel and vacuum lines are detached. It should only let gas flow freely in the PRI setting yes?
I did inspect the diaphragm and it looks fine but I don't have much petcock experience. I'm also gonna strip/clean and re-coat the tank. I'll use MEK to, hopefully, remove the Kreem and then muratic acid and possibly electrolysis to remove rust—which is present. I'm planning on Red Kote to seal.

In addition to all of this I'm gonna clean up all the electricals, connectors etc, testing with a multimeter as I go. I am also considering new Dyna ignition coils but I'm not sure if its necessary.

Anyways, I would greatly appreciate any wisdom regarding these undertakings. Most of this is new to me; while I have been learning a great deal from this forum and the web on whole, I'm sure there are plenty of details I'm missing. I'm ordering parts etc. now and researching. Is there anything else I should look into replacing that is not very expensive/involved?

Thanks for any input!!!
 

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It all may seem a bit overwhelming at times, but eventually all will sort itself out and you'll be good to go. Expect to have at least one issue arise for every year you ride her. That's how it's been for me the past 9 years with my Gpz.

All- in- all worth it IMO.

Any time you run into a problem feel free to e-mail me. I"m certain there is NOTHING that you will run across that I haven't as well.
 
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