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Thread: Another missing thread.

  1. #1
    Junior Member Supergoose's Avatar
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    Another missing thread.

    Bought a new 2014 last September. I live and do most of my riding at sea level or just a few hundred feet higher. So, obviously, it was running way too lean initially. I rejetted the carb in October and the bike's been running really well ever since. Well, until a few weeks ago.

    In the past few weeks, the bike has developed a really annoying misfiring condition when the engine is under load. It's most noticeable during acceleration but it's also very evident when running at highway speeds. I had to spend a couple of hours on limited access highways in NJ yesterday and it was really bad. Around town at relatively low RPMs it's hardly noticeable at all.

    The engine really starts missing when I'm accelerating and the revs get up past 7000. Trying to maintain highway speeds at >8000 RPM, the misfiring is almost constant, resulting in a really jerky ride. This situation seems to have gotten worse as the atmospheric temps (and humidity) have gotten higher. It really seems like a fuel delivery problem. It's almost like the bike is running out of gas, always. The V-twin engines on many of our mowers at work seem to develop a similar condition when the temps get hot which I've always attributed to some sort of "vapor lock". Oftentimes, cracking the fill cap on the gas tank alleviates the problem. Not too easy to do that with the locking cap on the TW.

    Before I start pulling the carb and tinkering with it or taking other complicated measures, just wondering if anyone else has any ideas of something relatively simple to try? I've tried a few simple things already, like filling the tank with 93 octane or adding a few tablespoons of Sea Foam. Didn't really expect either of those things to work and, needless to say, I wasn't surprised by the outcome. Checked the spark plug as well and the electrode is black but not filthy or wet or oily and the gap was fine.

    I just turned 4000 miles on the clock yesterday and I know that the valves are due to be checked but I can't imagine that this is attributable to incorrect valve lash? I suppose it's possible.

    I really appreciate any ideas anyone here has. Between the misfiring and my old helmet digging a furrow in my forehead and the crappy surfaces of the NJ and PA highways, I was fixing to lose my mind by the time I got home yesterday!

    Thanks.

  2. #2
    Senior Member scotti158's Avatar
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    I would check the valves. change the plug, and drain the float bowl to see if there is any water in the gas.
    2013 Yamaha TW200

    1996 Yamaha TW200

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  3. #3
    Junior Member Supergoose's Avatar
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    Thanks. I'll try all those things. Gotta check the valves anyway and plugs are cheap. After reading some more posts here about similar issues, I think I'll try a higher dosage of Seafoam as well.

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  5. #4
    Senior Member peter's Avatar
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    As Scotti said, adjust the valves and use the magic Seafoam. I also ride at sea level (only). Never touched the carb and still on factory jetting. Got now 22,000 miles on one of my TWs. I do adjust the valves almost (if I don't forget) every 2,000 to 3,000 miles and add every second tank (if I don't forget) about 2oz Seafoam.

    I also experienced the misfiring a while back but it was during deceleration. Again, valves and Seafoam, problem solved

  6. #5
    Junior Member Supergoose's Avatar
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    Thanks guys! I actually gave it three ounces of Seafoam yesterday evening and it seems to be running a lot better this morning. I'm not surprised the carbs have gotten crapped up. The bike sat for a long time last winter during the snows and (for a while anyway) I forgot to shut the petcock. Fuel sitting in carbs turns into varnish as we all know and it's starting to look like that was what my problem was. I'm guessing after I do the valves this evening, it'll be running like new.

    This place is a great resource for info. Thanks for everything.
    littletommy and SanDue like this.

  7. #6
    Senior Member admiral's Avatar
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    Do tell us what your long term results are. There is so much going on here which "could" be the culprit. The bike sitting for a while with the petcock left on does point very strongly to some clogged jets. Hopefully, your seafoam treatment does the trick. Checking the valves is another easy thing you could check, even if you think the seafoam has fixed it. I've had 2 TW's with the first one having two engines. Between the 3 engines, I've only had to "adjust" the valves 1 time, and it was just one of the valves. Some folks seem to have to adjust their valves all the time, but I must be luck as they don't seem to go out of tolerance very often and I check them all the time. Also, make sure to check your air cleaner.

    Good luck and again let us know if the seafoam (carb) was the only issue, or if valves out of adjustment could have contributed to the problem as well.
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  8. #7
    Junior Member Supergoose's Avatar
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    I'll definitely give an update after I check the valves and give it a chance to prove itself for a little while.

    Stay tuned for more action!
    admiral and plumbstraight like this.

  9. #8
    Junior Member Supergoose's Avatar
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    After checking the valves (they were still in spec, though a little tight) and running three ounces of Seafoam through a full tank, the misfiring condition seems to have completely disappeared. Seems those tiny little jets were just gunked up. Now I have a fuel economy question but I'll start a new thread for that.
    littletommy and SanDue like this.

  10. #9
    Senior Member Fred's Avatar
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    The small nylon screen above the float needle's seat are known to clog up with varnish also contributing to fuel starvation symptoms. So do the nylon screens above the petcock but they have vastly more surface area than the float needle screen. Glad the solvent/detergent approach has saved you a carb disassembly, 'tis my favorite type of maintenance....Seafoam it and ride,ride,ride!
    littletommy and SanDue like this.
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