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Thread: High idle, only sometimes when restarting warm engine on cold day (??)

  1. #1

    Question High idle, only sometimes when restarting warm engine on cold day (??)

    This is a slightly long story, please bear with me..

    I decided to adjust the throttle on my Street Triple for the first time. There was too much free play, maybe almost a centimetre. I watched a video on YouTube on how to do it, rode over to the local 2 Rinkan to buy some wrenches, and did it in the car park.

    I adjusted the cable at the handlebar end only. After adjusting it to a point that felt reasonable (roughly 4-5 mm of free play) I did up the lock nut again. Started the engine in the car park, and wheeled the bike around in neutral at idle, turning the handlebars a couple of times to full lock in each direction. The idle was normal, and didn't vary with the angle of the handlebars. It felt much better on the ride home.

    The next day (Saturday), I went for a longer ride. For the first half of the ride, no problems. Rode in normal traffic to the coast, then along the 134 and up the Yugawara Parkway. Took a lunch break in the mountains, then down the Mazda Turnpike, and started home along the expressway. Stopped in at a service area for a coffee.

    After 20 minutes or so, I went out to the car park and started my bike. This was when the trouble started. Straight away, it was idling high, around 4000 RPM. According to the temperature gauge the engine was still warm (no surprise), but the air temperature was pretty cold. It was a bit embarrassing to ride through the car park like some kind of baka gaijin bosozoku, but there wasn't much traffic in the car park. Soon I was back on the expressway, so no problem. By the time I exited the expressway half an hour later, the problem had gone away. Idle was normal at traffic lights. I thought no more of it.

    The next day (Sunday), I started the bike from cold. No problem! It just did the normal auto-choke thing, then normal idle. Again, it was a very cold day. I rode about 20 minutes in traffic, then parked the bike. Went for a walk, 30 minutes or so. Came back to the bike, engine still hot according to the temperature gauge, and started the engine. And.. again, the 4000 RPM idle! Turned the bars from lock to lock, forced the throttle shut, gave it a fistful, restarted the bike. No change. Nursed the bike home, doing my best to avoid red lights. The problem remained the whole way home, until I stopped the engine on the way into my car park.

    Since then, I've ridden it to work and back every day this week, with no issue! No high idle at all!

    The only difference I can see between my commute and weekend rides, is that on weekdays I'm always starting the engine from cold in the morning and in the evening when I go home.

    It's not a huge problem, but it makes me nervous (I've been carrying the wrenches around with me everywhere I go just in case). I'm sure it's something to do with me adjusting the throttle, but I don't know what I've done wrong. I'm pretty sure I didn't over-adjust it. I could always make it slack again, but.. that kind of sucks :) I'd like to try plugging a USB OBD doo-hicky into it to see if the throttle and temperature sensor readings make sense, but I don't have one.

    Suggestions for this mechanically challenged rider please!

  2. #2
    Join Date
    Oct 2013
    Location
    Kawasaki
    Posts
    273

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    How long have you had the bike? Is it possible it existed before?

    I don't know about modern bikes. Could it be a sensor not reading right? A temperature sensor or something?

  3. #3

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    Thanks for the reply!

    I've had the bike nearly 3 years, so it's definitely a new thing.

    Yeah, it feels like an intermittent bad sensor reading to me too. Seems like too much of a coincidence that I recently adjusted the throttle though.

    I went to the Triumph shop near my office to ask if they'd heard of it. The owner told me that the throttle position sensor sometimes needs to be re-zeroed after adjusting the throttle cable. Doesn't explain why it happens intermittently, but I'll take her word for it and get them to do it next time I take the bike there.

  4. #4
    Join Date
    Jan 2017
    Location
    Machida
    Posts
    23

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    Quote Originally Posted by arber View Post
    Thanks for the reply!

    I've had the bike nearly 3 years, so it's definitely a new thing.

    Yeah, it feels like an intermittent bad sensor reading to me too. Seems like too much of a coincidence that I recently adjusted the throttle though.

    I went to the Triumph shop near my office to ask if they'd heard of it. The owner told me that the throttle position sensor sometimes needs to be re-zeroed after adjusting the throttle cable. Doesn't explain why it happens intermittently, but I'll take her word for it and get them to do it next time I take the bike there.
    Have you lubed the cable? I realize going to 4k on the dot everytime may be a stretch for coincidence but you never know.

  5. #5

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    Thanks for the suggestion. It seems to open and close pretty smoothly, and doesn't feel like it's getting stuck anywhere. Strangely I can't find instructions for lubing the throttle cable in the workshop manual - only an adjustment procedure.

    The problem hasn't happened again, so I'm going to wait and see for now. Thanks for the help so far!

  6. #6
    Join Date
    Jun 2013
    Location
    Sagamihara-shi
    Posts
    717

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    Exhaust sensor going bad?
    Bit of advice, Never create a forum account and screen name after drinking heavily and imagining stupid shit you would like to do before you die.

  7. #7

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    Which cable did you adjust? There are usually 2. One is the close cable and the other
    the open cable. The way to adjust it, irrespective of youtube, is to take the play out of the
    open line and check bars lock to lock, but keep play in the close line. If both cables are
    a little tight it will cause sticking of the throttle. I suspect you don't have any slack in the
    close cable and when the bike is warm it is pulling against the open cable.
    Apexmoto Inc - Dyno tuning, engine/chassis/suspension upgrades, repairs, shaken, tires & changing with balancing, graphics printing, stickers, media blasting, painting & powder coating.

  8. #8

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    PKF, I hope it's not an exhaust sensor, that sounds spendy..

    Jav, thanks for the tip! I could only find one adjuster near the bars, and I think it's the open cable. I'll take a closer look when it's light, try to find the close cable, and make sure it's got some slack. Thanks a lot!

  9. #9

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    Quote Originally Posted by arber View Post
    PKF, I hope it's not an exhaust sensor, that sounds spendy..

    Jav, thanks for the tip! I could only find one adjuster near the bars, and I think it's the open cable. I'll take a closer look when it's light, try to find the close cable, and make sure it's got some slack. Thanks a lot!
    I have an ST in my shop. Just checked and does look like the adjuster is on the open cable.
    As mentioned, though you need to make sure the close cable has a little slack, with bars full right.
    Good luck.
    Apexmoto Inc - Dyno tuning, engine/chassis/suspension upgrades, repairs, shaken, tires & changing with balancing, graphics printing, stickers, media blasting, painting & powder coating.

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