Thunderbird 900 Sprag Clutch Question

Discussion in 'Thunderbird' started by Ian Suggett, Sep 2, 2017.

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  1. Ian Suggett

    Ian Suggett New Member

    Aug 22, 2017
    27
    3
    Durham
    Quick question

    Did Triumph fix the issue with the Sprag Clutch on later models of the Thunderbird 900?
    I'm about to pick up a 2003 bike and wondered if it was something that I should be concerned about as I seem to remember reading something about the later models being unaffected?

    Thanks in advance

    Ian
     
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  2. stevethegoolie

    stevethegoolie Elite Member

    Oct 16, 2014
    2,091
    800
    East Riding of Yorkshire
    As long as you keep the battery in top form then you should be okay. Yes, they were uprated some time in 1994 I do believe (but will stand being corrected) and failures on these later bikes, whilst not unheard of, are unusual.
    I'd like to think that a 2003 model would be a safe bet.:)
     
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  3. Ian Suggett

    Ian Suggett New Member

    Aug 22, 2017
    27
    3
    Durham
    Thank you, I always have my bike plugged into a battery conditioner when not in use. Might replace the battery also just to be on the safe side.
     
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  4. capt

    capt Noble Member

    May 8, 2016
    1,613
    450
    western Australia
    The problem wasn't the sprag clutch or the battery . All the early triumphs pre 1994 were, supposed to have an ECU that prevented spark/ignition firing until engine had done TWO full rotations, so engine was spinning over quickly, there was a stuff up from the ECU suppliers, and, this wasn't happening!! So what happened on some bikes(causing sprag clutch to break) was ignition firing when engine cranking speed was to slow(back firing) this put too much load on starter system and the weakest point broke (sprag bearing), ECU's were replaced @ services, problem solvered !!! I had 94 Trident with this problem. ECU was replaced @ 40 odd thousand klms.

    Cheers capt
     
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  5. Petrol

    Petrol Member

    Sep 18, 2016
    43
    18
    North Wilts.
    I fitted the later ecu and the starting was completly different. The early one starts immidiatly , fine if the battery is 100 % . The problem comes from if its not and as the engine turns over it cannot get it over compression , the engine goes in reverse and it is this that kills the sprag clutch. The later ecu has to see 200 rpm minimum before the ignition is enabled.
     
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  6. KjellB

    KjellB New Member

    Jul 1, 2019
    21
    3
    Norway
    Hi
    Where did u buy the later ecu and part no ? Thanks
     
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  7. Godders

    Godders Well-Known Member

    Apr 29, 2019
    123
    83
    Keith
    I had a '96 sprint and still have a 1998 TBS and have never had issues.

    Don't know if it is true but heard a rumour that the earliest models (pre 1995) could be repaired more easily / more cheaply as there was access within the cases to effect a repair, whereas with the later versions of the earlier engine it necessitated an engine out and split of the crankcases. Is that true?
     
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  8. sprintdave

    sprintdave Nurse,he's out of bed again
    Subscriber

    May 25, 2014
    1,211
    450
    Birmingham
    Yes that is correct.
     
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  9. capt

    capt Noble Member

    May 8, 2016
    1,613
    450
    western Australia
    I think the original part number should get you the right ecu/controller, the problem was the early supplies. Was fixed late 94 early 95 so check dates of manufacture/supply on the ecu
     
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  10. Alatamoc

    Alatamoc Active Member

    Mar 29, 2019
    99
    28
    Uk
    Thanks chaps....I too have had an interest in the 900's but been put off by Sprague clutch problems.
    Now I know the ' safe' years to look for.
     
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  11. sprintdave

    sprintdave Nurse,he's out of bed again
    Subscriber

    May 25, 2014
    1,211
    450
    Birmingham
    You mean safer. They still can give probs if the battery is weak. Mine is a 95 and it needed the spray doing a few years back.
    It isn't just a triumph issue either, many other bikes suffer the same
     
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  12. Godders

    Godders Well-Known Member

    Apr 29, 2019
    123
    83
    Keith
    So in fact the easiest bikes are the safest to buy due to the cheaper fix
     
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  13. Godders

    Godders Well-Known Member

    Apr 29, 2019
    123
    83
    Keith
    Earlier rather than easiest. Bloody predictive text.....
     
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  14. Alatamoc

    Alatamoc Active Member

    Mar 29, 2019
    99
    28
    Uk
    Oh dear...back to the drawing board then.....
     
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