Carburettor Thunderbird 900

Discussion in 'Technical Help' started by dieselian, Apr 30, 2022.

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  1. dieselian

    dieselian New Member

    Apr 30, 2022
    4
    3
    Switzerland
    Hi there,
    I have just bought a Thunderbird 900 of 1995 that has been standing for around 10 years.
    There was loads of deposite in the carburettor and after an ultrasonic treatment and renewal of the o-ring sealings of the float chambers as well as the rubberparts linking the carburettors and an adequate and careful assembly the carburettors are leaking. What can be the reason?
    Another question:. I would have the opportunity to get a full rack of carburettors of a running but newerThunderbird Sport. Would this fit on an ordinary older Thunderbird?

    Thanks for your help

    Jan
     
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  2. sprintdave

    sprintdave Nurse,he's out of bed again

    May 25, 2014
    1,339
    750
    Birmingham
    Q1 when you say leaking do you mean overflowing? If so did you check/replace float needles? Kit available from sprintmfg.co.uk.
    Q2 Sorry don't know but would expect them to fit with changes to jets, needle position etc. Are they the same diameter?
    I see this is your first post, why not introduce yourself in newbie section and show us a pic of the bike.
     
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  3. dieselian

    dieselian New Member

    Apr 30, 2022
    4
    3
    Switzerland
    Hi Sprintdave,

    Yes I mean overflowing. The Bike is actually at a friends place who mainly does the work on it so I can't take pictures. Thanks for the link to: sprintmfg.co.uk. but there must be a typing error, there is no page opening. On the original Triumph part list there seems to be only the complete floater. I just join the pdf.
    I will present myself once taking the time to understand how to do and when I'll have pictures.
    I bought my bike some weeks ago (for around 1000£) but am not really sure if it has not been a mistake as the parts here around are so horribly expensive. Eg. for 3 pilot jets and 4 little rubber parts between the carburettors I paid £150...
    All the best

    Jan
     

    Attached Files:

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  4. Adie P

    Adie P Crème de la Crème

    Jul 7, 2018
    3,478
    1,000
    MID DEVON
    Good morning Jan.

    First, welcome to the wonderful - but often very difficult - world of Triumph T300 ownership!

    (In case you're unaware of the background, the term 'T300' is used to define the early '90's range of triple cylinder motorcycles made by Triumph, Hinckley and coversmodels such as Trident, Trophy, Tiger, etc.)

    Second, you need to be aware that this range of motorcycles has, largely, been out of production for more than 20 years so I'm afraid it's inevitable that spares will often be difficult and scarce to find. That in itself has the effect of keeping spares (new and used) prices high, often shockingly so, and you will need to be prepared to do a lot of searching of both wallet and soul if you want to stay in this non-exclusive 'T300 club'! I would add that the rewards of membership can be equally high when you actually get to experience the visceral emotions of owning and riding a machine that has so much of that over-used term 'character'!

    OK, to your current situation.

    First, this link should take you to Sprint Manufacturing

    https://www.triumphparts.co.uk/product-category/triumph-parts/triumph-all-parts-stocked/

    Sprint have a good stock of new and used parts and are (in my opinion) by far the best "independent" supplier of parts for the early Hinckley models.

    Second, this link will take you to the page for carburettor parts for your model of 900 Thunderbird.

    https://www.fowlersparts.co.uk/part...-carburettors-t1240930-t1240194-t124064030656

    Fowlers are a main dealer and distributor of genuine factory Triumph parts and their mail order service is usually excellent - other main dealers and distributors are available but I have always had good experience with Fowlers and can recommend them.

    You'll notice that the float assembly (item number 19 on the drawing) for the carburettors on your machine cost almost £38 EACH and, with postage, you'll be looking at over £120 excluding any import duty that might be applicable in Switzerland! As I said earlier, these bikes are NOT cheap to own and run!

    Which leads me on to the slightly more technical side of your post - i.e. the carburettors and overflowing fuel. Fuel overflowing from the carbs is most likely to be one of 3 things :-

    1) float chamber gasket(s) leaking
    2) float ruptured
    3) fuel inlet valve not fully seating

    Pretty much regardless of the specific cause in your case, I would suggest that the carbs will need to be removed and re-cleaned. You don't mention if you changed the float chamber seals but, with the other work you mention having been done, I would think this might be a good starting point in looking at this particular problem.

    On the question of whether carbs from a TBS will fit, from memory, I think the TBS carbs are a different make and type so jetting will probably be completely different. The Sport engine delivers almost 20% more power than the 'standard' T'bird models and I imagine some of that gain comes from carburation changes. While the TBS carbs might physically fit the mounts and may even work, I suspect that it will need a mountain of tuning work - and replacement parts - to get them to run properly.

    If the TBS carbs you have access to are good and reasonably priced I might be interested and maybe we could work out a mutually beneficial trade with Sprint parts?

    I do hope that you get the T'bird up and running and can enjoy some of the real pleasure and delight of owning and riding one of Hinckley Triumph's finest!

    Good luck and do, please, keep us updated.

    Adie
     
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  5. sprintdave

    sprintdave Nurse,he's out of bed again

    May 25, 2014
    1,339
    750
    Birmingham
    Sorry about the sprintmfg, forgot it was triumphparts as I have saved it as a fave and don't look. They list or used to, float needles and gasket sets and their prices are always better than OE parts.
    As stated fowlersparts.co.uk are very good and cheaper than World of Triumph too.
    For carb bits there are also
    allensperformance.co.uk
    nrp-carbs.co.uk
     
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  6. dieselian

    dieselian New Member

    Apr 30, 2022
    4
    3
    Switzerland
    Thanks for your detailed answers. I am aware that the Thunderbird is almost 30 years old and that parts have their price. When I was talking about exageration in Switzerland I meant that I was asked Chf 144 for rubbers that Triumph-parts.uk sells £7,95...
    As the type of floater of the earlier carburettors does not seem to have replaceable needles I will probably need to order new ones. I will have a closer look tomorrow.
    Cheers

    Jan
     
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  7. dieselian

    dieselian New Member

    Apr 30, 2022
    4
    3
    Switzerland
    P.S. concerning the Sprint carburettor rack, I saw it on ebay for 250£
     
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  8. dirty big hands

    dirty big hands Active Member

    Aug 4, 2017
    183
    43
    sussex
    How do you mean "leaking" ?

    If it's when on the sidestand, engine switched off, the left hand float bowl gets flooded by the other 2 and fuel leaks into the airbox.
    You need to switch the fuel off at the petcock and let the levels in the float bowls drop a bit before switching the engine off.
     
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  9. dieselian

    dieselian New Member

    Apr 30, 2022
    4
    3
    Switzerland
    Hi, thanks for your answer. It is overflowing due to old o-rings and probably the floating needles. I shoud get the super repair set from Sprint Manufacturing and report the results.
    cheers
    Jan
     
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  10. dieselian

    dieselian New Member

    Apr 30, 2022
    4
    3
    Switzerland
    Hi there,
    the super repair kit responded to its promise. The girl is finally running! 10 years of abandon had left some traces and asked for patience.

    But now I discover and I should probably open a new thread for that: there is once cylinder having regular misses due to valve play I suppose. Does anybody have a listing of the valve tolerances and the torque rates when wrenching all together again? The model is the Thunderbird 900 built in 1995.

    Cheers

    Jan
     
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  11. Adie P

    Adie P Crème de la Crème

    Jul 7, 2018
    3,478
    1,000
    MID DEVON
    Hi Jan.

    It's probably worth your while buying one of these :-

    https://www.ebay.co.uk/itm/313536454950?hash=item49003aa126:g:A-8AAOSwPZpgpp5a

    or one of these :-

    https://haynes.com/en-gb/triumph/thunderbird/1995-2004-0

    Clearances should be measured cold and are quoted with a range :-

    Intake clearance is 0.10 - 0.15mm or .004-.006in.

    Exhaust is .15-.20mm or .006-.008in.

    I think the aim is to be somewhere mid to high range since (I understand) the clearaces reduce overtime.


    A real expert will be along shortly to correct any inadvertant errors! ;)
     
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  12. Erling

    Erling Elite Member

    Dec 12, 2017
    1,118
    943
    Norway
    Great to hear that you got the cards sorted. And a valve check is never wrong. I'd have an eye open for coil problems too though. If one cylinder is acting up I would move the coils around to see if the problem follows the coil or is consistent to one cylinder. If new coils are needed, a stick coil conversion is recommended. And easy.
     
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  13. dieselian

    dieselian New Member

    Apr 30, 2022
    4
    3
    Switzerland
    It does not seem to be an ignition problem. But he valve play is definitely out of tolerance. Let's see what thicker shims do.
     
  14. dieselian

    dieselian New Member

    Apr 30, 2022
    4
    3
    Switzerland
    Now the shims are adjusted, valve play is ok, ignition is ok too, but the engine does not start any longer. I have checked the fuel arrival, all ok. What can be the reason?
     
  15. sprintdave

    sprintdave Nurse,he's out of bed again

    May 25, 2014
    1,339
    750
    Birmingham
    If it was running before, though with the occasional miss, I would guess you have either shimmed the valves wrong or done something else. Go back and check everything again. Check coils too by substitution, faulty cps? You say fuel is ok so writing that out for now but needs check maybe?
     
  16. dieselian

    dieselian New Member

    Apr 30, 2022
    4
    3
    Switzerland
    Hi there,

    I'm about to despair.
    I got the engine running (with difficulties) but it does not turn over 2500rpm. Once warm it is easier to start but still not turning over 2500rpm. The ignition is checked. The carburettor is clean. The idle jets(40) are changed, the main jets are free. I wonder if there is too little resistance in the replacement air filter. Or could it be the carburettor valve not lifting completely? The diaphragm seems to be tight.
    Help!!!!
     
  17. sprintdave

    sprintdave Nurse,he's out of bed again

    May 25, 2014
    1,339
    750
    Birmingham
    I wouldn't think the air filter would make that much difference tbh. Can you take the airbox out and check the butterfly valves in the carbs are opening fully?
    Dont know about the diaphragm, sorry.
    Fuel starvation? Blocked filter or tap.
    Throttle cable problem?
    Going back you had it running but missing sometimes, did it rev up fully then? If so you need to go over everything you have done and re check. Are you sure you have done the valves correctly, never done them myself but know some people have got it totally wrong, did you follow a manual?
     
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  18. capt

    capt Elite Member

    May 8, 2016
    2,999
    750
    western Australia
    The diaphragm rubbers maybe shot !
    If they are leaking , they won't lift the throttle body pistons ?
    Just a thought , you've had something apart that hasn't been touched in year's and probably wasn't designed to last anywhere near that long ...!
     
  19. dieselian

    dieselian New Member

    Apr 30, 2022
    4
    3
    Switzerland
    The diaphragm rubbers seem really fit. My next thought has been that outworn admission rubbers disturb the correct carburettor function, but after putting new ones on it there was still no change. The engine starts difficultly and does not turn over 3000rpm
    My latest discovery is that there is not only suction but also blowing on the air admission when the engine turns at idle. I will have to re-check the valve play and if the valves move freely. Unfortunately the ignition timing (my other thought) is checked on a running engine...
    I've bought the Haynes online manual actually to be OK with the specs.
    I'll report
     
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