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Discussion Starter #1
Hi folks!

I got my GPZ500S '92 (~20.000km) about this time last year, and it ran great the whole season. It spent 3 months in a garage during the winter, and since then it's been acting up. I changed a sparkplug, and it ran great for about a month or so - then it broke down.

This is what happens: the engine stops firing on the right side, and gasoline starts running out the carbs. The local Kawasaki dealer took a look at it, but was ready to give up on it (now this apparently is a _really_ lousy mechanic) but changed the sparkplugs and reconfigured something (that needed some vacuum-thing) and it ran for another two weeks.

.. then it broke down again. I came back, and after a bit of convincing, he decided to accept more money from me (aargh?!) and check out the carbs. He found nothing out of the ordinary, but after this the bike ran fine for a couple of weeks.

.. then it broke down again. I thought it was time to get a new mechanic, and since I was all out of Kawasaki dealers in town, I talked a Yamaha mechanic into taking a look at it. He messed around with the carbs for a couple of hours, and told me that he'd "fixed the float-thingy". I didn't really care what he fixed, because the bike ran again. I rode a couple of hundred km's on it, and a few hours ago it started spewing gasoline again.

My mechanic budget is seriously blown for this year, so I expect this will come down to me, a screwdriver, a wrench and my Haynes manual. My question now is this; has anyone experienced a similar problem, and do you have any advice? Maybe a checklist of some kind?

I'm kinda desperate! :cry:

Cheers.

(Note: right sparkplug soddy - left one nice and white)
(Edit: GPz500S == EX500A)
 

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FLOAT

Still sounds like a float sticking...soak your old spark plug overnight in white vinegar to get the junk out of it and then blow it out in the morning, reinstall it...take an extension for a socket wrench or a screwdriver and use the handle to tap the bowl on the carb when it starts acting up, then with fresh gas(I hope you were using fresh gas and not the old gas as it will sour and not function properly) and perhaps just a shot or two of alcohol to clean things out as you ride. IF this doesn't clean things out then you will be pulling the carbs off and rebuilding them. Freakinout has a carb rebuild link or an attachment, just PM him for it...
 

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Discussion Starter #3
Re: FLOAT

ZX-2R said:
Still sounds like a float sticking...soak your old spark plug overnight in white vinegar to get the junk out of it and then blow it out in the morning, reinstall it...take an extension for a socket wrench or a screwdriver and use the handle to tap the bowl on the carb when it starts acting up, then with fresh gas(I hope you were using fresh gas and not the old gas as it will sour and not function properly) and perhaps just a shot or two of alcohol to clean things out as you ride. IF this doesn't clean things out then you will be pulling the carbs off and rebuilding them. Freakinout has a carb rebuild link or an attachment, just PM him for it...
Thanks for your reply! Since the bike was stored, I've refuelled it several times - so any sour gas should be long gone. What puzzles me, is that mechanic #1 cleaned out the carbs (or that's what he said anyway) and mechanic #2 "fixed the float", yet the carbs still seem to be the problem? I'm guessing here, but could it be dirt in the tank? There are no gas filters installed on it.

Could a sticky float be the reason the right plug gets black? I know for sure I can get the thing running with a new plug, but these last months experience tells me that it's only a question of time before the plug dies on me again and gas starts leaking out.

I'll soak the right plug tonight and try the tap/alcohol tomorrow and let you know what happens.

Thanks again! :)
 

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Discussion Starter #4
Update

I just went down to rip out the plugs, and I couldn't resist trying to fire it up. As I hit the starter, I tapped on the carbs, just to see if it had any effect (I've tapped before, but VERY lightly - which apparently has no effect what so ever) - and it worked! Sure, the bike isn't happy, and slightly dark smoke came out the right exhaust, but it started nevertheless. I've soaked the plugs now, and hope the bike is up for a 20km ride out to my dad's tomorrow - then we'll try to give it a complete overhaul, install gas filters and maybe clean the tank with diesel.

I'll keep you posted.

UPDATE: There are two fuel lines from the tank - should I install filters on both, or is there a smarter way?
 

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TWO LINES

YOu have two fuel lines...one to each carb?
YOu should have right out of the tank only the one. I'd ssiphone some gas out into a clean jar or glass container and se if you have any scum or anything in tank...if so then slosh it out and clean it good then fill it up...sounds like the carb could be getting something in it from the tank...having a good filter is smart, if you can find one that will fit and is NOT plastic... We could get pretty deep into the carb because the needle valve and the seat could be worn slightly or even have some sediment literally stuck not allowing the needle to properly seat, or as silly as it sounds even the float can hang up, but riding vibration ans such should clear it up. Check th make sure tha tyour airfilter is really clean, and that it is (like ours is really oiled) properly seated...dust gets past it and you have problems with it getting into the carbs...if the one carb keeps sticking you could pull the plug on the bottom of the bowl an suse something like acoffee filter so seee if ther is any junk coming out then turn the petcock on and let some gas pass through...then, if you were to turn off the petcock you could carefully figure out a way to spray carb cleaner in and then open the petcock to dilute the strong carb cleaner...then button it up and try to run it again. Till you either get it running right you may have to carry a screwdriver in your pocket to tap the carb...until you can take thenm off and rebuild them...find Freakinout as he has a carb rebuild link or attachment that is VERY detailed...and let me know it the shot of alcohol in the tank works. SOme people swear by using Marvel Mystery Oil in their gas tanks as it "lubricates" the top end. Simply putting some 2 stroke oil or even a small amount of diesel in the tank will do the same thing...the good part is that it also passes through the carbs cleaning them as it passes through.
 

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Discussion Starter #6
Re: TWO LINES

ZX-2R said:
YOu have two fuel lines...one to each carb?
YOu should have right out of the tank only the one.
The petcock (I'm new to these words, but it's the on/res/off gas valve, right?) is mounted directly on the tank, and two rubber hoses (different thickness) goes from the valve to the top and bottom of the carbs. According to the Haynes manual, one of them is a vacuum pipe? I'm still clueless as to what this is, but I expect I'll have to put a filter on the one that leaks gas when I turn the knob :)

I'm learning at lightning speed here.. hehe :D
 

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Gas filter

yes, OFF ON REServe. Even though there is a fine mesh screen in the bottom of the tank, It is easier to toss a fine filter than to clean the tank screen...and keep a spare in plastic somewhere on the bike, (when it would only fail away from home.) You have a fine motorcycle...!
 

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Discussion Starter #8
Re: Gas filter

ZX-2R said:
yes, OFF ON REServe. Even though there is a fine mesh screen in the bottom of the tank, It is easier to toss a fine filter than to clean the tank screen...and keep a spare in plastic somewhere on the bike, (when it would only fail away from home.) You have a fine motorcycle...!
The bike survived the trip out to my dad's place today, and we took the thing apart. The slim hose between the tank and the carb was indeed for the vacuum-valve (or whatever the word is) that is part of the petcock thingy. We blew the carbs clean without disassembling them totally, filtered the gas through a coffee filter (no point in spoiling a comlpetely new gas filter), and installed a (plastic) gas filter afterwards. We picked the filter (and a replacement O ring I needed, a couple of plugs just in case and a little fuel pipe) at a out-of-town Kawasaki dealer, that turned out to be waaay cheaper than the two other places in town where I went earlier.
When asked if plastic was a bad idea, he said no (some info on why picking plastic filters is bad would be great). I explained my problems to him, and he advised us to inspect the fuel inlet needles and see if they had any scratches or grooves. No visible wear/tear was seen, but the needles wouldn't seal off the intake completely, until we had blown the whole thing clean. I expect a very small grain of dirt was blocking it. We inspected the coffee filter after pouring all the gas through it, and found a little dirt (we're talking grains smaller than fine sand here, but a little nevertheless).
Other than this, the air filter was checked (and actually glued together, since it was all brand new, but had come off the plastic frame a little in one side) and the cables were oiled.

Anyway, the bike runs smoothly now (or atleast the 20km's home) and I'm actually a little optimistic about the whole thing. In conclusion, the problem must have been dirt in the carbs, and the solution a gas filter. That's my theory anyway. I'm clueless as to why none of the mechanics I went to installed a gas filter.
 

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DUST/DIRT

Great to know that you have it in running order! My objection to plastic is that it not only melts, but cracks, and depending upon where it is placed rubs and can also...like on an automobile engine never be polaced inbetween the pump and carb ecause it will act like a Capacitor in an electrical circuit...you let off on the gas and it bulges, you stomp the gas and it contracts...it literally attenuates the effects that you want. when you want full throttle you dont want the balloon effect fo the plastic you want the constant full pump flow from the fuel pump directly to the carb...I like the aluminum and glass, or brass/bronze and glass filters for gas...something not expanding and contracting...and it should be directly from the tank... I'm tickled that yo have the motorcycle spinning like a top again...keep us informed and please don't be shy or a stranger now that you'll be spending more time on the bike than off...You'll have to tell us about some of the roads that you ride!!!
 
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