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Discussion Starter #1
I've ridden my '89 ZX600R for about 5,000 miles now, and throughout that time, the engine has run flawlessly. This spring I had the spark plugs and oil changed, ran better than ever. I've ridden it a fair bit since then and it's always been great. The other day I took it to work and it ran normally. Then, 8 hours later, when I started to leave work, the engine sputtered and died a minute after I'd started it. It took about 5 minutes before I could get it to start again, at which point it ran fine. No noticeable loss in power, and it pulled cleanly. I rode it for about 10-15 minutes, and then I pushed it a little bit on the highway. Middle of the highway, the engine just died. I couldn't get it to start for another 10-15 minutes or so. Again, after I got it started, performance seems at or near what it was before. Ever since then, the bike is hard to start - not crazy hard, mind you, but it takes a good few seconds of cranking and twisting the throttle, whereas it always started on the first try without throttle, every time, before. This is true whether the motor is hot or cold. The exhaust also seems to smell more of gasoline than it did before, making me think that maybe it's suddenly running too rich. Once started, the bike runs fine, except for the gas smell. I rode it a good 100 miles today under all kinds of load, and it ran well. I don't have fuel consumption figures, because my trip meter doesn't work.

Any ideas as to what could have caused this sudden degradation in my engine? When it started happening, my fuel was fairly low, although not nearly as low as I've had it at other times. I wasn't even on reserve yet. Since then, I've filled the bike up at a gas station that I know to be good (been getting gas there fairly regularly as long as I've had the bike). It hasn't changed anything that I can notice. Other than that, there were no unusual circumstances surrounding the time when the bike started acting up. The choke, as near as I can tell, works like it always has. The cable isn't sticking or anything like that, and the bike will happily idle at its normal idle speed once I get it started. Throttle response is crisp from off-idle to redline.

Any ideas as to what's wrong with my bike? Thanks for looking.
 

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Discussion Starter #3
One of my first thoughts was also the vent tube. However, I opened the gas cap when the bike died on me and that didn't seem to do anything.
Also, if there is a restriction of gas to the engine, why would the exhaust smell MORE of gas than it did before? Isn't that a sign of running rich, or am I mistaken? It was also my understanding that if there's a restriction of gas, the engine will act up under load and/or high RPM. This is not the case. Since the two original stallings, about 20 minutes apart from each other, I've ridden the bike for a few hours and the motor acts consistently: harder to start (need to crank about 5 seconds while giving gas, hot or cold, choked or not), exhaust smells of gas, but runs just fine under all speeds and loads, with maybe just slightly less power in the very bottom end, but that could just be my imagination, it's that minimal. I don't feel qualified to determine whether it's lost power in the top end at all, but it definitely still pulls strongly and cleanly.

Thanks for the reply. All input is appreciated.
 

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you might be getting weak spark. maybe loose battery connection or coil connection. tighten everything up, clean your air filter. make sure your battery is filled and charged. Winters are hard on batteries that's why you see lots of them failing in the spring.
 
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