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Thread: carb issues

  1. #1
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    Default carb issues

    All I am really needing to know is which way to turn the air/fuel mixture screws on the carbs to lean it out as currently she running a bit rich aka there is littraly fuel coming out of the cans haha

    i set the carbs to what the sigma jet kit said to do and she has not been running right since, Well tbh it was never running right since i got the bike in the first place so thats why i jetted it and stuck a rebuild kit into the carbs but nothing has changed she is still down on power and bogging down even at the slightest of throttle movements.

    The haynes book of lies dosent tell me and i found this pdf online so ive set the screws to these specs tonight and ill take it for a run tomorrow to see if its cured but just in case i need to know which way is which with the screws I assume in is air out is fuel?

    900ss Tuning a carburetor.pdf
    If it Dosent rattle .....Somthings broken!!

  2. #2
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    Hi Wulfie,
    Turn the screws out (anti-clock) to richen the mixture. They usually run best at about 3 to 4 turns out. I do it by ear, but try 3 1/2 which I found gave the best results.

    Old enough to know better, young enough not to care

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  4. #3
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    I've got one of those colortune tools if you want a lend of it buddy, can post it up.

  5. #4
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    Well I fitted a stage three sigma jet kit and the instructions said three turns out although I'm finding the ends on the cans wet with fuel. Idles fine revs fine at a standstill but out on the road give it any throttle it just dies feels like it has no power at all either.

    Starting to get really fed up with it now.
    If it Dosent rattle .....Somthings broken!!

  6. #5
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    If it is idling well then the issue is not with the mixture screws, they only affect the idle and just off idle throttle. The next stage is the slides and needles. Being CV carbs of course it's not quite straightforward. Firstly are the diaphragms ok? No holes in any of them? Are they fitted correctly? Is the small o-ring in place under the diaphragm cover? Have the springs been changed or are they OEM? Are they fitted correctly? (I don't think you can get them wrong)
    I don't think the needle and needle jet should have much effect below 1/4 throttle but as well to check it out. Your kit probably supplied a different needle and gave a recommended position for it, probably the middle notch which would be a good place to start

    Old enough to know better, young enough not to care

  7. #6
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    I did fit new diaframs to the carbs as the old ones we knackered I didn't touch the adjustment on the needle as it was set what the kit said it should be set at the springs are OEM but seem fine and I was pretty careful about putting the tops back on with the o-rings.
    If it Dosent rattle .....Somthings broken!!

  8. #7
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    The only adjustment available is the pilot screws, try adjusting 1/2 in each direction and see if there is any change. Sorry I can't think of anything else.

    Old enough to know better, young enough not to care

  9. #8
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    Which ones are the pilot screws? I've been looking at so many diagrams they all seem to be worded differently.
    If it Dosent rattle .....Somthings broken!!

  10. #9
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    Item 14 in the drawing, on the underside of the carbs, sometimes known as air screws or idle mixture screws.

    Old enough to know better, young enough not to care

  11. #10
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    So update I ended up putting everything back to standard configuration. Airbox, sidepods and the long Remus cans put the standard jets back in the carbs..... Still running bad. I took the plugs out today as I could not get it started it was poping and banging. Front one looked good back one was black as night wet looked like oil or drenched in fuel I cleaned them and put the plugs in the ht leads and burled it over now I have no spark at all for the vertical cylinder the plugs are fine they both work well in the horizontal HT lead maybe this is all just a spark issue still. Although I have not acquired an oil leak from the horizontal cylinder now also.... It's never ending with this bike I just want to enjoy the sunny weather and it's fast becoming an expensive ornament. *Cry*
    If it Dosent rattle .....Somthings broken!!

  12. #11
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    You seem to having a real run of bad luck with this bike. Perhaps the trouble has been ignition all along.
    Since bth plugs spark on the horizontal I think we can rule out the plugs.
    So firstly, swap the ignition igniter boxes. If the spark swaps to the horizontal cylinder it's the igniter.
    If still no spark on the vertical swap the coils. If it changes to the horizontal it is the coil that is duff.
    If no change then the pickup is faulty. The pickup resistance should be 100Ω 5%.
    You should also check for 12v at the brown wires to both coils and both ignition units. Since they are all connected to the same 2 pin connector it is very unlikely that one of them isn't getting 12V but it's possible that one of the pins in the ignition unit connectors isn't fully home.

    Old enough to know better, young enough not to care

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