Really bad breakup off idle
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  1. #1
    Junior Member fatallightning's Avatar
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    Dec 2015
    Nyack, NY

    Really bad breakup off idle

    Been chasing the issue for a couple weeks now, and throwing parts at it is getting old. Last couple rides, the bike was starting to act strange, down on power, choppy, popping notably more on decel. It will start and idle fine, as soon as I give it throttle, it wants to sputter out and die. Sometimes I can get it to sort of rev if I get past the lower range dead spot, but its still a mess. Up to this point, I've put about 3500 miles in 2 years on it problem free. Immediately noticed that the black ground wire that grounds onto the ignition coil had rattled the bolt loose and wasn't grounding at all. Weirdly, the bike still ran. Fixed that, new plug. No difference. Cleaned the old plug, put it back, and it seemed ok for one ride. Then bad again. I've taken the carb apart about 3 times for cleaning, also just changed the low speed jet for a fresh one. New ignition coil, and just did a new CDI as well. Bike is an 87. Valves haven't been checked in a while, nor the cam chain. Gonna do that tonight. It almost seems to me to be ignition timing. Where should I start checking in the other electrical components?

  2. #2
    Senior Member tylermoney's Avatar
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    Mar 2019
    Austin Tx
    It's likely that something went missing when you took apart the carb?

    That's what I discovered at least. The first time I took the carb apart, I hadn't realized that a tiny spring went flying across my garage never to be found again. When I put the carb back together and reinstalled on the bike, I had a similar issue to what you're describing. I had a forum member remind me to double check that I didn't loose a specific tiny spring that sets the needle in place under the spring seat cap. Turns out I had lost it. My problem was solved one I got a replacement and reinstalled.

    My bike is a 2019, so a different carb style, but there are still those little springs that are easy to lose. Hopefully it's something that simple. Here is a diagram of the '87 tw carb:

    Good luck. I hope you find your issue without too much more hassle.
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