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Discussion Starter #1
I just purchased a 2000 ZX-6 with less then 5000 miles and am having troubles with keeping it running. The person I purchased it from only put 100 miles on it last year. At higher RPM's it seems to have good response but is doggy and will stall at low RPM's. Even while driving on the highway while running 5000-6000 RPM, it starts to spit and sputter and will loose power. I've taken the carbs out and checked and cleaned the jets and put fresh fuel in but still the same problem. I have a new fuel and air filter on the way hoping this will help and the plugs were changed by the seller when I picked it up. When the carbs were off, I could see a lot of carbon build-up on the valves. I called a local mechanic and he suggested having "the carbs. syncronized and ride it hard to get the carbon off. If the carbs. are clean and the fuel is fresh, it shouldn't need a valve adjustment with this few miles." Does anybody have any suggestions? I'm slowly learning how it all operates.
 

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Discussion Starter #3
Thanks for the advise, I ordered a carb. synchronizer and will do this when it comes. I was working on the bike again and am getting closer to the problem. I found if the gas tank is not hooked up and the bike is only running off the gas in the bowls, it idles perfect. The gas pump can then be heard cycling. When the pepcock is turned to "ON or "RESERVED", the pump is no longer heard cycling and the bike will slowly die after 10-15 seconds. After shuting the gas off, restarting and hit the accelerator a few times, it idles fine again. Any suggestions???? Is the pump bad or does it have a vapor lock type problem? Can Bypass the pump?
 

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CARBON and Wierd running

FIrst thing I would do is to run a DIFFERENT type of gas through it and make sure it is 91 octane...second thing that I would do is to run a different set of plugs. If you have carbon anywhere on the plug or even inside like on the valves it gets hot and wierd things happen. I'd be running the stock plugs and running the bike harder in rpm's, to get it blown out if you can. I'm not sure about running Marvel Mystery Oil in the gas...it may be an old farmers trick, but I am sure about running a little diesel. It will make the bike run hotter, but it will definately blow the carbon out. If you have an old farm truck, or and old car that has been driven slowly for long periods and miles you can definately clean it out with diesel. ON cars and trucks you can pour about 4-6 oz of it in while holding the throttle open enough to keep the engine running fast and it will smoke like you wouldn't believe and leave all sorts of black soot all over the ground behind the exhaust pipes. I've never tried it on a bike, but I wouldn't think that adding a little diesel in with the fuel would hurt anything...ask a great mechanic about it, but beware using to much of it could definately ruin an engine! READ the plugs and change them! Another thing to check maybe first is to put some soapy water in a spray bottle (dish soap and water) and spray around your carbs, gaskets even your airbox to see if the idel increases. IF it does then you have an air leak.
 

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Discussion Starter #5
Thanks for the advise. I may have to give this a try. I did however put fresh plugs and gas in prior to your reply. My next question is how important is the vacuum system? I've read other suggestions in the forum and with your reply it sounds like even a minor leak can cause problems. Since I cleaned the carbs, I've been running the bike without the air filter box in place because I am waiting to get my new air and fuel filter. Could this be the cause for the problems I am when the petcock is turned "ON"? Does the bike need that vacuum to pull the fuel from the tank? I am also awaiting a service manual for the bike so I get a better understanding of how it all operates.
Thanks for the replies guys!
 

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The vacuum in carbs is necessary. By running the bike without air filter is very dangerous for your engines health. Or did I understand that you had your filter on, but no air filter box? Of course if you didn't have neither, the underpressure in the carburator venturi is very low. That is why when you ride it on higher rpm's, it sounds like everything is allright. The air is moving faster then. But when you're idling, the air is standing almost still when your carbs are wide open in the venturis other end.

Check for air leakage. When you had your carbs cleaned, did you install them properly? Where there any o-rings to be changed? Any cracks on intake rubber seals? Did you clean the jets only or the whole carburator, even the float bowls? Did you fasten every nut and bolt with the right torque (usually means not left open)?

Have you had your fuel tank pepcock open? Might be that it's wrongly assembled. Sounds like it at least. You mean, when you put your pepcock "OFF" the fuel pump starts cycling? And when "ON" or "RESERVE" it stops? Is the pepcock somehow connected electrically with the fuel pump? Is the fuel pump before or after the pepcock?

My guess at least, check the air leakage but ONLY after you got your air filter and box in place.

BTW. There are different kind of chemicals to be poured in your fuel tank and are supposed to extract the carbon build-up. Try them to get your engine clean (or ride it hard).
 

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Discussion Starter #7
I decided to try bypassing the fuel filter and fuel pump assembly and gravity feed gas directly from the tank to the carbs. Bike idled great with no hesitation in accelerator. For some reason when the pump is put in line with the tank, the motor will stall yet it sounds like it is cycling. I've been testing this without the air box/filter in place. I've checked the voltage at the connector for the fuel pump and it reads 9-10Vdc, is this normal? If a fuel pump fails, what are the symptoms and can they become air locked from disconnecting the main fuel supply? Do they need to be primed?
 

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FILTER

YOu cannot run the bike without having the filter box or some air resistance at idle or you will be running way to lean..it will not operate right in any event. IF you have a plastic filter toss it and replace it. It acts like a rubberband or capacitor in an electrical circuit. the minute expansion contraction of fluid pressure will effect your performance..If you are running a filter it should be before the fuel pump. Like Strictly VN 1600 said you may want to take apart your petcock and check it out for proper operation and make sure that it is flowing properly in both ON and RES positions. IF you were to install a free flowing airfilter and had a free flowing exhaust, or ANYTHING in between you would have to change the jetting appropriately. Like Freakinout using K&N air pods (seperate air filter for each carb) and having an aftermarket free flowing exhaust, he had to rejet his carbs (stage 3) and adjust things accordingly. I'd ask about the Vdc on the fuel pump as it may change with the rpms of the bike and whether it is using Vacuum or only Vdc to force/pump fuel. What ever you get done, let us know and keep us updated...
 

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Discussion Starter #9
OK guys, here is the progress as of last night. My new air and fuel filter game in so I slapped everything back together. I previously had taken the petcock apart and it was clean, full running in both positions. When I put the bike together, I bypassed the full pump running the fuel line from the tank, threw the filter, in the carbs. I did this because the bike idles fine without the pump in the circuit and when I ohmed it out, there was only 1 ohm of resistance. I tried contacting a couple dealers but none had it in stock to verify resistance. Anyway, once the bike was together, I topped off the gas, 91 octane, and turn the pepcock on. I was then on another project and later noticed a puddle of gas under my bike. Looking through the fairing, I saw gas leaking from where the brass nipple comes from the carb, this is controlled by the choke. I also saw through the window my crankcase oil level increased and smelt like gas. What I believe is going on is fuel is being pushed past one of the seats in one of the carb. bowls and overflowing into the engine and crank. Sound Logical? This is why it runs like crap with the pump, it's overflowing the bowl and flooding the engine causing it to kill at low RPM's(FYI-I powered the pump up out of the circuit and could feel it cycle so it must be working). I won't be able to verify anything until my manual comes and I learn how it operates. Do you typically leave the petcock "ON" from day to day or shut it "OFF" everytime the bike is off?
 

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PETCOCK

Absolutely shut it OFF! As the temperature changes especially if you've been outside in the sun the tank will cause the pressure inside the tank to expand or contract. That is why some of the guys on the web have asked about a whining noise from their tank. It is more common when the tank is near empty. At least you are making some progress and starting to KNOW your bike...
 
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