Tps And Ultrasonic Carb Cleaning.

Discussion in 'Technical Help' started by Pike, Oct 2, 2019.

  1. Pike

    Pike Member

    Sep 25, 2018
    62
    18
    Bristol
    Have been riding the Bonnie for couple of weeks now. It is running great except it occasionally cuts out. This happens when idling e.g. at traffic lights. Not all the time and more prone to happen if on incline, up or down hill. Starts up then rides and pulls v well. Symptoms usually is a drop in idle to about 900rpm then dies. If you notice it and blip throttle, it will settle back down to normal idle and not die. Could it be float heights? Pilot screw adjustment? Any advice appreciated.
     
  2. Callumity

    Callumity Elite Member

    Feb 25, 2017
    3,358
    800
    Nr Biggar
    I am not sure if you have a tacho and have your idle set accurately at 1050/1100 rpm.
    A variable idle in such a simple motor with Efi gizmos comes down to things like sticky throttle cable and linkage operation, inlet air leaks that minutely lean out the mixture (check for perished vacuum caps on inlet manifolds), throttle synch and pilot air screw setting (2.5 turns out). The easiest way to check for inlet air leaks on a running motor is soapy water or a WD40 spray forward of the carbs. It might just be a stumble if the tickover is marginally too low.
    Additional possibilities? Malfunctioning SAI or nipped tank vent pipe.
     
  3. Pike

    Pike Member

    Sep 25, 2018
    62
    18
    Bristol
    You adjective of a "stumble" is exactly how I would describe it. Its carb engine BTW. I set up carbs as per jenks bolts performance and pilot is 2.75 turns out. Not a massive issue but will check for air leaks.
     
  4. Callumity

    Callumity Elite Member

    Feb 25, 2017
    3,358
    800
    Nr Biggar
    You might be a smidgen lean at idle ......
     
  5. Wire-Wheels

    Wire-Wheels Elite Member

    Apr 26, 2019
    2,497
    800
    California - USA
    Interesting. As far as I can tell, mine has no TPS. but it is a first year [2002] U.S. Federal Spec. bike. All it has electric on the carbs are the heaters. ...J.D.
     
  6. Callumity

    Callumity Elite Member

    Feb 25, 2017
    3,358
    800
    Nr Biggar
    It’s the black plastic thingy on the forward outer edge of the RH carb with a wire leading back under the side cover.
     
  7. Wire-Wheels

    Wire-Wheels Elite Member

    Apr 26, 2019
    2,497
    800
    California - USA
    You are correct. I went out and took a look. It is there. Learn something new everyday, if you pay attention :) ...J.D.
     
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  8. Callumity

    Callumity Elite Member

    Feb 25, 2017
    3,358
    800
    Nr Biggar
    Now funnily enough my carb heater is fried and I have never noticed its absence ......
     
  9. Pike

    Pike Member

    Sep 25, 2018
    62
    18
    Bristol
    After running the bike for a good few weeks I decided I would look at making some minor adjustments to the pilot air mixture screws to remove the occasional "stumble" to below idle I had been experiencing. To facilitate this and for easy access whilst in situ, I have fitted some knurled thumb screw types. OK this did involve having to remove the carbs....again.... to fit but now I can make minor adjustments accurately and with little fuss. I have gone back to 2.5turns out and there is no more "stumble" so far. Whether it's the slight adjustment of number of turns out or achieved a perfect air tight seal from all rubbers when reassembling is a mute point. Happy anyhow and running sweet.
     
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