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Engine cutting out under heavy throttle

Discussion in 'Technical and Troubleshooting Torque' started by Azamakumar, Aug 10, 2011.

  1. Long and the short of it - wind the throttle on and bam engine's dead. Usually when I've just hopped on, after warming it up. Had the same problem a few months ago and it went away by replacing a battery that was on its last legs. I'd guess the same problem this time round but I'm fairly sure that these things are meant to last far longer than a few months with near daily use. I'll be picking up a multimeter on the way home so I can properly diagnose the battery before forking out for a new one.

    I'm ruling out a loose connection with a battery terminal because lights/dash/whatever are still running when the engine goes. It doesn't clutch start either when this happens, I've got to pull the clutch in and whack the starter which fires it up instantly. Is it possible the HIDs have done a number on the battery (it's a yuasa ytx, possibly 14-bs)? Only recently put them back in because I didn't have em mounted properly initially and didn't have the time to pull the front end apart, probably about 2 weeks ago, and this has been happening for around a week. It usually fires up on the first or second crank when cold.

    It happens less the longer I've been riding, but the tacho does seem to dance around a bit under heavy throttle. So yeah, is a rooted battery doing this or is there another problem?
  2. You dont say what your bike is but I have come a cross some bikes that dont like HIDs. The last one was a CBR600 2007 that refused to fire up until the motor had spun over about 10 times. I pulled this bike apart until I got to the point where the only none standard bit was the HIDs. Removed them with the lights back to standard and it never did it again. I've researched HIDs affecting ignitions and found no info giving a reason why they would mess around with the ignition signal and I also know lots of bike with them fitted that have had no problems, so is it the HIDs or not? not too sure.
  3. It's a 2009 hyosung GT250R. The dancing tacho only happens when the HIDs are switched on (the bike has a headlight switch). Engine cutting out happens when they're off as well.

  4. I'm definetely not that mechanically skilled but from reading just the title I initially thought that the choke may be a culprit (choke on, twist throttle, runs too rich and cuts out). After reading though about the tacho playing up definitely sounds electrical.

    Just thought I would mention it just incase.
  5. Not the choke.

    Sending me nuts because both home and work are ~1km from the onramp to the M4, so I'll lean in on the onramp and open it up and it cuts out, or I'll pull out to overtake someone and get nada. Probably leaving the bike at home til it's sorted.

    :( just when it warms up
  6. is your bike injected does it have a throttle position sensor etc etc
    we need MORE INFO.
    if it was a battery last time check your terminals make sure they are tight, check your charging system cheek and see if it's a short with your headlights . Electrical gremlins are horrid and hyo electrical gremlins are par for the course.
  7. Interesting diagnosis E2W, the only thing I can think of is that HIDs by their nature will be more electrically noisy in the radio spectrum. If this noise is impressed back on to one of the sensors for the Engine Management Unit, i.e. crank position indicator, O2 sensor etc it could confuse the Engine management.

    This probably applies to cheapo HID kits more than quality ones. I am interested to hear others experiences with these.
  8. Sounds like it's running lean, strip & clean the carbs as a start...

  9. Could be a fried reg or battery terminal. The headlights take load when they are on, but nothing to take load when the lights are off.

    My initial thoughts would have been carby, but the above comment is based on the headlights being a real symptom.
  10. @smee: it's carbed. I've given the terminals a once over but like I said everything else still has power

    @ibast: I can easily rule out the headlight, but it still happens when it's not making a load
  11. The fact it doesn't clutch start also points toward reg or alternator.
  12. when I was first looking at getting a bike, I checked out the hyosung's. I did a lot of reading, and came across an issue where they would often cut power under acceleration. Anyway, after much wailing and gnashing of teeth, it turned out that they had a faulty side stand sensor. I believe they fixed it on newer models, but you may have one of the dodgy ones.
  13. How would I check the reg? The one I had on the first one went after a couple of months.
  14. Multimeter. Check the battery stopped, idling and revving. Pay attention to what the headlight does when you rev too.

    Sidestand could be right if it's happening when moving only.
  15. I'm with Ibast then I reckon the reg may be dying.
  16. Actually may be sidestand, had it cut out when I kicked it into gear after work today.

    Won't have a chance to get a multimeter before I head home so I'll take a dig at the switch tonight.
  17. Does the engine simple cut out dead/stoppped/nothing, or is it more like a spluttery loss of power? It could be the ignition leads that need replacing.
  18. Not the rectifier :(

    12.99 @ off
    12.98 @ idle
    13.48 @ 6k rpm

    What else is there?

    EDIT: did another test, 13.2 with all the lights on
  19. side stand note : had a gsx750f and found it cut dead and I shat as you can understand 100 and no power and cages all round honking and almost ramming.
    If while you are riding and it cuts, kick at the side stand to lift it up a notch, if that kicks it again then you found the problem. Mine had a slightly bent and worn pin/bolt and it would cut when going over a bump and get a slight jolt, enough to breack the contact..