1994 carb troubles
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  1. #1
    Noob! Greenz1000's Avatar
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    Aug 2019

    1994 carb troubles

    Hi there,

    new to the forum so please bare with me. Iíve recently acquired a 1994 speed triple 900 from my dad, after my z1000 got stolen at the beginning of the year. Anyway since Iíve had it Iíve done a full service on it, oil, oil filter, changed back to original air filter from k&n, new plugs, brake fluid, clutch fluid, antifreeze basically the full works. Now since Iíve done this it has been running a lot better and Iíve also been running it on super unleaded as my dad hadnít ridden it for over a year so the petrol was getting old. Iíve only done around 100 miles on it since doing the service. Anyway recently weíve been on holiday and every day Iíve had off since Iíve either been busy or the weather decides to turn for the worst.

    so I fired her up for the first time in probably 1.5 months last Friday and it struggled to start and then it wouldnít stay running unless I held the throttle open slightly. Once warmed up it would stay idling fine but when you revved it the revs would shoot up. Then suddenly a big pool of petrol appeared underneath coming from the join between he air box and the air intake. Now this bike had done this previously when my dad owned it but I assumed it was a stick float valve in the carb. Could this be the same thing?

    Ive read a lot about the seals breaking down inside the carbs causing similar problems. So could that be a possibility also?

    They are mikuni carbs, BST 36mm I think.

    I am a car mechanic and have previously stripped down car carburettors but I donít have the tools to re sync them. Iíve seen you can buy float bowl kits that come with new float valves and all the seals required. If I was to strip them down and fit all the seals would I then have to get them balanced again or should they be ok?

    sorry for the very long and thank you for taking the time to read it. I hope someone can help as I have a day trip planned to the isle of weight at the beginning of sept and I canít risk it as it is now.

    Thanks in advance.

  2. #2
    Noob! Broken Wings's Avatar
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    Mar 2020
    Cocoa Florida
    You can buy a vacuum balancer on *bay for cheap. There's even a YouTube video that shows how it's done. If you don't have time there are a couple outfits that will hot tank and rebuild/bench test them for you.

    It's cheaper than buying a power commander and a laptop......

  3. #3
    The "Friends" of Officer Frank Poncherello Chewie.'s Avatar
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    Jan 2006
    Melbourne, Victoria Australia
    Common problem due to the age of the bike. O rings on the float valves have perished. You can't buy the o rings separately, you'll need to buy three new float valves. Bugger of a job but it will solve your issues.

    "I haven't shot anybody since 1992...and even then I didn't do it!" - Mark 'Chopper' Read

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  5. #4
    The "Friends" of Officer Frank Poncherello dr_gallup's Avatar
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    Jun 2006
    Upstate SC
    I've never even seen the carbs on a ST but on some bikes I've worked on the carbs are all mounted on a bracket and opened by a linkage. On those, you can pull the whole assembly off the engine, flip it over and work on the floats without affecting the sync. Of course, given the age, they probably need to be resynched anyway. Not a big job if you have the vacuum gages.

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