pmot

I just bought this bike and it ran fine when i test drove it. after a while of riding it just lost power. Eventually after this happened a few times i noticed the transparent fuel filter had hardly any fuel in it. I started tracing this problem back and today I "disabled" the automatic fuel shut off so it flows freely when in the on position. I also fixed a fuel leak in the line. I was riding it around today at low speeds on gravel just to see if i fixed it. After about 20 miles I looked at the transparent fuel filter and saw that it was almost empty again. so I headed back home while it was still running fine. Once I got home I took it down some asphalt and opened it up because I was sure that once I did it would run out of fuel and cut out like usual. Sure as poop it did, but I could have ridden it around all day at 40mph and it would have never acted up ( maybe it would have but at low speeds i did not have any problems with it for 50 miles and I would get into the throttle a little bit to get it up to speed.) I experience fuel starvation after a while at speeds above 50mph and can experience them more rapidly if I am in the throttle a lot say 90mph or so. I have concluded from this that the fuel tank is not getting quick enough relief from pressure, which is obvious. At low speeds there must be at least a leak fast enough for the fuel to keep up with the motor, but once you open the throttle up and, according to my theory, create a negative pressure in the fuel tank so great that no matter how slow you drive I you still can not get enough fuel into the carbs. I allow it to sit open the tank and when I am off again it runs fine, but not for long , depending on how I drive it. I have eliminated the posibility of it being the automatic fuel shut off. How do I further narrow down my problem with the same lack of cost as my automatic fuel shut off delete. How does the pressure relief system work in this fuel tank? I hear talk of replacing the seal and making sure my relief line is not clogged, but what are some other possibilities? It can't be hard but I have little knowledge in this area.

Dablue1

If your bike is a 2000 or newer model, it should have come with an in-line filter. It's very small, and is located in the fitting on the carb end of the fuel line. It's very hard to see, and most people don't even know it's there.

Some aftermarket inline fuel filters can impede fuel flow because the hole in the nipple maybe too small. The fuel system on the Ninja is a gravity feed system so the fuel needs to flow freely with the petcock in the normal running position. any one position will allow the fuel to continuously flow and possibly flood the engine with fuel.

You can switch to another make of filter or use the stock one. If your bike is relatively new and the tank is clean, the stock fuel filter along with the microscreen inside the tank should catch most debris.

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pmot

yeah ok but fuel is not even getting to the aftermarket in line fuel filter installed in between the pedcock and carb as mentioned in the novel I typed above. I can tell because it is transparent and i can only see a couple drops in the lower corner when it cuts out. Maybe when this problem is fixed I can worry about the filter by the inlet or poor sizing of the aftermarket filter but for now I just want the bike to run properly. The bike is an 05 with 4400 miles

pmot

because there is so little fuel in the in line filter I traced the problem up to the pedcock, which I cleared as an issue, so I am lead to believe now that the problem is in the tank or with the vent.

Dablue1

Is your vacuum line properly attached to the petcock? Have you removed the filter and attached it straight to the carb? Try that and see what happens

pmot

No you do not understand, maybe I did not explain it well enough. You see I "modified' that pedcock so that it would flow weather the engine was running or not as long as it was not in the off position and it does just that. I have yet to try and see how long it will flow before the negative pressure in the tank gets too great. perhaps that will be my next experiment that way I can open the tank to relieve the pressure once the flow stops. Then I can further trouble shoot. Just so I make myself clear, the pedcock is not the issue. at least I have disabled that vacuum actuated automatic fuel shut off by removing the O ring and spring so that even if it did shut it still would flow fuel through. After I did this I proved my theory by opening the pedcock and letting fuel run out for a short period of time just to prove to myself that It did not now (after my modification) need any vacuum from the motor to supply fuel to the carbs. Therefore I concluded that the problem was a negative pressure in the tank. Sorry if I'm being repetitive.

pmot

As far as the filter goes its new I just bought it after first experiencing problems. Also like I said before I can see only a couple drops in the transparent filter and that is actually before it would pass through the actual filter material inside the transparent case. I can assure you that the problem is not in any way the filter or the vacuum actuated fuel shut off.

pmot

and is this tube on top of the crank case go to anything or does it just vent into nothing?
061202_190601.jpg picture by pmot_album - Photobucket

Dablue1

That is the crankcase vent tube. If you have the airbox installed, it attaches to the bottom of it.

pmot

So I left the gas cap open today and rode it around and it was horrible. Usually it runs fine till I get on it but this time it was trash until I got on it supper hard and then it would have a serge of power before falling back on its face. there was still very little fuel in the transparent fuel filter. (just to recap, the automatic fuel shut off has been modified so that if flows freely in the on position running or not, and the fuel tank was open so there is no issues with a negative pressure in the tank.) I also made sure fuel was flowing properly to the carb by removing the line from the carb and emptying a good portion of my tank into a gas can. I am now lead to believe that there is a positive pressure coming through the carbs and pushing fuel back into the tank or at least putting large amounts of air in the line. The only explanation I can think of is a poorly sealing intake valve. Please let me know what you think of my theory.