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Discussion Starter · #1 ·
I got a 97 Ninja 600R a couple weeks ago. I got it cheap because its been down. Everything was fine on it for a while. It took me a long time to figure out why, but sometimes my bike will miss out really bad around about 5-6 grand. I finally figured out its only after you fill it up with gas. If it has a half tank, it will run fine. If you go fill it up, it will cut out real bad. Any ideas? Also, when you are cruising at about 40 mph, the front tire wobbles. If you let go of the bars it will wobble like crazy and probaly end up wrecking. It doesnt do it at any other mph. Im guessin it needs balanced. But if you could help me on the rough running problem i would greatly appreciate it. Thanks
 

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second chimp in space
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My guess for the cutting out is that your tank vent isn't venting for some reason. The little hose might be kinked, or there might be dirt or something else blocking it in there. While you're in there, also check the two hoses between the tank and carbs for kinks: fuel line and vacuum line.

As for the wobble, it could be the tire, could be the steering head bearings, or it could be uneven fork oil levels.
 

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Discussion Starter · #3 ·
Ok ill check that out. Its weird because it only runs rough for about the first half of the tank. Anyone know the top speed of this bike?
 

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second chimp in space
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I've had that happen with my vent. It's all about air pressure. Pretend you don't have a vent. If the tank is full and you're using up gas, you have less gas and still the same amount of air. So that air expands to fill the void, lowering its pressure. This makes it harder for the gas to flow (because where it flows to is still atmosphere pressure), and eventually it will even stop. If you have half a tank full, then there is much more air in there, and it will take MUCH longer for you to use up enough gas for the air pressure to be low enough. And since you still have some venting, you may never reach a point where you notice.
 

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I don't think uneven fork oil levels would cause such a wobble. There are many bikes that use cartridge dampers in one fork leg, and standard oil damping in the other, and they don't have issues although they have different suspension properties between the two legs. Also, I rode my GSX-R1000 over two weeks with one blown fork seal and there wasn't any abnormal wobbling, only softer suspension characteristics.
 

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second chimp in space
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happened to me. my one fork seal was blown for a good while, and i had barely any oil left in there towards the end. Wobble got progressively worse as the oil leaked out. After new forks (old ones were pitted), wobble went away. So yeah, i suppose it could be that the old forks were bad in some other way, but i couldn't find anything wrong with them save the pitting. Bike was an '87 ninja 750.
 

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enos said:
happened to me. my one fork seal was blown for a good while, and i had barely any oil left in there towards the end. Wobble got progressively worse as the oil leaked out. After new forks (old ones were pitted), wobble went away. So yeah, i suppose it could be that the old forks were bad in some other way, but i couldn't find anything wrong with them save the pitting. Bike was an '87 ninja 750.

Hmm, well I can't deny that it couldn't happen then. I just figure that a wobble is a side to side movement, which the forks are not a part of. I would think that maybe forks that were not damped would exaggerate or amplify an existing wobble problem maybe. I dunno.
 

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Discussion Starter · #8 ·
It only happens at 40 mph. As for the miss in the engine would it work if i left the gas cap loose? Just to see if that fixes it? Thanks for the help guys.
 

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Are you sure it's 40mph, or is it an actual throttle opening? Ususally drivability problems are Engine RPM related, or throttle position related.
 

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As for your front end wobble I experienced the same problem between 40 and 50 mph, I took it and had tires balanced that seemed to help a little, but not completely, so I replaced head bearings and now everything is just fine.
Good Luck :fiddy
 

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second chimp in space
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Redstar11 said:
Hmm, well I can't deny that it couldn't happen then. I just figure that a wobble is a side to side movement, which the forks are not a part of. I would think that maybe forks that were not damped would exaggerate or amplify an existing wobble problem maybe. I dunno.
It could be that I had minor tire or head bearing issues that I didn't notice after the new forks. Odd thing was that it also happened around 40mph. Fork oil level is pretty easy to check, and its prolly a good idea to check it anyway...
 

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Discussion Starter · #12 ·
Well, im not sure about the shake in the front. It really doesnt bother me. But the miss in the engine drives me nuts. Just tonight it was running perfect, i was almost ready to hit reserve. I filled up, and then it ran like shit. I checked all the gas lines and vents, they seemed fine. Any suggestions?
 

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When you run your tank to near empty, does it HISS when you pop open the gas cap?
 

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Can you describe the 'cutting out' a little better? How long does it cut out? What RPM are you usually at? Is it like a bogging sensation?
 

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enos said:
I've had that happen with my vent. It's all about air pressure. Pretend you don't have a vent. If the tank is full and you're using up gas, you have less gas and still the same amount of air. So that air expands to fill the void, lowering its pressure. This makes it harder for the gas to flow (because where it flows to is still atmosphere pressure), and eventually it will even stop. If you have half a tank full, then there is much more air in there, and it will take MUCH longer for you to use up enough gas for the air pressure to be low enough. And since you still have some venting, you may never reach a point where you notice.
Thanks for that response.. may be why mine isnt getting fuel... looks like i need to drain and clean it.
 

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This is the reason why I asked you if the tank hissed when you popped open the gas cap. If it doesnt hiss, then you don't have a pressure difference between the air in the tank and atmospheric pressure, and therefore no vacuum lock on your tank.

So, if it's not hissing, then what ENOS described is probably not your problem.
 

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second chimp in space
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yeah, but there is no problem when the tank is emptyish. Does it hiss when the tank is close to full? Or better yet, run it until you notice the sluggishness, then quickly pull over and open the tank.
 

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Or better yet, run it until you notice the sluggishness, then quickly pull over and open the tank.
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Good idea.
 

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Discussion Starter · #20 ·
It will miss out when you fill it up with gas. Like it runs fine to the gas station, then when you take off from the gas station it will miss out. I know it sounds like im crazy. It does it about 5-6k rpms if your taking off fast, but if you just kinda take off slowly it will miss out a little. It just isnt smooth.
 
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