Triumph Bonneville 2001 Start And Idle Problems

Discussion in 'Technical Help' started by TraiaRider, Jul 5, 2025.

  1. TraiaRider

    TraiaRider New Member

    Aug 4, 2024
    1
    3
    Sweden
    #1 TraiaRider, Jul 5, 2025
    Last edited: Jul 5, 2025
    I have a Triumph Bonneville 2001 and have had crud in my carbs problems.
    It ran only with choke/enrichener enabled but pretty good then.

    I tried running Red Line SL-1 additive
    to clear out crud in the carburator and it was succesful at first. I didn't have to run with choke/enrichener engaged. After a short period of time it developed a leak that got worse and worse. Still it ran OK allthough gas was collecting on the top of the engine.

    One morning it was suddenly hard to start and I drove only for a km and it stopped and wouldn't start anymore. I figured the leak was running haywire with the vacuum and so set about to dissasemble the carburators. I belive the leak was in one end of the T-junction for the inlet of petrol. Changed the o-rings and applied a new gasket for the floatbowl. Cleaned the carburator and parts in a sonic sound cleaner. I could then see through the idle jet, no problem. I also applied the Dynojet tuning kit with a new needle and with what they call DJ110 main jet. The idle jet is still the original one.

    I followed the instructions and set the idle screws to 3 turns out. (They were set at 4 turns out before cleaning procedure, I checked)

    I assembled the carburators and mounted them on the bike. No more gas leakage. The leak was fixed. However it was very hard to start and when started it idled at high rpms. The engine dies intermittently. Does not give good response when I blip the throttle. Dies on to much gas. I can milk it a little bit.

    I tried to fiddle with the idle knob but when turned counter clockwise a fair bit the engine would die.

    The bike has TOR exhaust, the baffle in the airbox is out. It has the bellshaped mouth and high flowing airfilter for the airbox. 3 out of 4 vacuum caps are new and all of them are good so no problem there. It got a new fuel hose and new inline gas filter. Battery is new and was hooked up to charger during the carb cleaning procedure.

    Can this be helped by adjusting the idle screws? if so should I go in our out?

    The bike is undrivable at the moment.

    please help
     
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  2. Robbi18

    Robbi18 New Member

    Jun 15, 2025
    12
    3
    USA
    Since it’s idling high and dying on throttle blips, your pilot circuit might still be clogged or the idle screws need tweaking. Try turning them in to 2.5 turns (from your current 3) to lean it slightly if it improves, you’re on the right track. If not, double-check the idle jet again sonic cleaning doesn’t always clear stubborn gunk. Also, verify the float heights and needle seating since you swapped jets. Hang in there it’s close.
     
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  3. TraiaRider

    TraiaRider New Member

    Aug 4, 2024
    1
    3
    Sweden
    I tried 2.75, 3.5, 4 and 4.5 turns out on the idle mixture screws and it felt like 4 was the best.

    It started quickly but idles very low and stuttery now on every setting. Dies intermittently.

    I push in the enrichener and pulled just a little wee bit on throttle and keeping the throttle here it runs ok for like a minute and then just stalls.
    I try it repeatedly and get the same behaviour all the way up till the engine gets warm and it continues after.

    More twist on the throttle and it dies immediately.

    Really weird.

    I also discovered that the original main jet was a 115 wich is the same as dynojet 110.

    I'll do what you ask and will clean out the idle circuit again. I will revert back to stock needle with what it ran well previously.

    Not sure how to check float height?

    What do you mean by needle seating? That I didnt forget the collar?

    I am on the right track you think and its not electrical?
     
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  4. TraiaRider

    TraiaRider New Member

    Aug 4, 2024
    1
    3
    Sweden
    I have now ascertained that the canals in the main circuit and idle circuit are free flowing.

    The jets and idle mixture screws are swimming in a jar of carb clean untill tomorrow when I will inspect them for flow.

    Needleseats are undamaged.

    I guess then I will assemble the carburator, leak test it and check petrol level in float bowl
     
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  5. TraiaRider

    TraiaRider New Member

    Aug 4, 2024
    1
    3
    Sweden
    The floatbowl heights was fine.

    I changed back to the original jets and needle.

    I have ascertained that the idle circuit and jets are free flowing.

    Now when I put the carbs back on with idle mix screws at 3 turns out
    the bike starts up fine but idles low.
    This was a warm sunny day.

    I tried different settings at 2.75, 3, 3.5, 4 and 4.5

    With a cold engine best idle was had at 3.5 and with a warm engine 4 turns out.

    But the sound on throttle is not good. When I try to drive it there is no power. When I pull of in first gear it almost stalls, feels like Im trying to start in 4th gear???

    The engine doesnt revv cleanly.

    The ignition does not cut out when getting hot.

    This set up was what the bike ran cleanly before. I feel like I have done what could be done with the carbs.

    What else can it be?

    What else should I try?

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  6. Boothman

    Boothman First Class Member

    Jul 26, 2023
    841
    500
    Wigan
    If not a fuel or spark issue what about air flow. Is the filter soiled or recently changed, is there anything obstructing air going in to the airbox?
     
  7. TraiaRider

    TraiaRider New Member

    Aug 4, 2024
    1
    3
    Sweden
    #7 TraiaRider, Jul 11, 2025 at 12:15 PM
    Last edited: Jul 11, 2025 at 1:14 PM
    I have not check the sparks and am not sure how to do that.

    I will measure ignition coils with an ohm meter. I dont believe my issue is with the pickup coils as it doesnt behave like the described issue with the engine cutting out completely when it gets warm.

    About airflow.
    I did take the baffle out. I have installed a new hiflo air filter and
    have the TTP breathe installed. With this configuration it ran fine for a long time. A bit jumpy at times and I did have to run with the enrichener engaged wich led me to do the red line sl-1 clean. And that in turn led to leaky carburators.

    With leaky carburators it still ran fine but lots of gas on top of engine.

    One day I ran for a km and it just stopped.

    When I removed carburators I can see to the airfilter from the airbox boots. Airfilter is like a half year new. There is in my opinion nothing that hinders air.

    I could fit back original triumph air filter and remove TTP breathe but doubt it will change anything.

    Air flow should be fine.

    Sparkplugs about half a year new and iridium type.

    I also sprayed WD40 on intake rubbers and around cylinder. Could not notice a rise in rpm:s,
    the idle was constant.

    How to go about checking spark?
     
  8. TraiaRider

    TraiaRider New Member

    Aug 4, 2024
    1
    3
    Sweden
    I did a little electrical measuring.

    At the connector to the ICU under the saddle I did two tests.

    In the third row, between pins 5 and 6 you can measure pick-up coil.
    Should be 550-650ohms, mine came out 589 (pic 1)

    I also measured the ignition coil
    between row 2, 2nd pin and row 3, 2nd pin. Should be about .5-1ohms
    and mine came out as 2ohms(pic 2)
    wich is close enough and not open circuit.

    3rd test was a measurement between spark plug boots wich is ok since it is configured in the wasted spark system . It should be 10-15kohms and mine came out
    12.01kohms(pic 3)

    I then proceeded to dismantle the ignition coil and measure on it directly.

    Primary(pic 4) should be around .7ohms and mine came out .8ohms.
    Secondary(pic 5) should be about 2.3kohms and mine came out 1.97kohms wich is close enough and not open circuit.
    It is a Gill ignition coil.

    Seems to me coils and HT-leads are OK.

    ICU has no indentation marks from saddle.

    Hopefully not ICU problem????

    F***!, Help!?

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  9. TraiaRider

    TraiaRider New Member

    Aug 4, 2024
    1
    3
    Sweden
    However now when I read up on the internet I came across this comment
    about failures in secondary circuit on an ignition coil.

    "But failure is usually only present when high voltage is applied in operation - a 'flashover' between winding turns."

    Maybe I need to try with a replacement?

    opinions?
     
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