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Pinned GSX250 - Air Intake - Exhaust - Caburettor Tuning

Discussion in 'Suzuki 250cc Twins' started by GreyImport, Jan 22, 2014.

  1. Ben Mulligan

    Ben Mulligan Well-Known Member Premium Member Contributing Member

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    Gents, I found that Peter Stevens have mikuni BS30SS Jets and they are relatively common. I've been offered a 120 jet which is a full size up for $10ea. Thats pretty good! Half sizes like 117.5 are $15ea.

    That should get me started, then I can check the more complex needle jets and whether the needle needs shortening.

    Also - The Motul rep told me about drilling a hole in the balance port so that the diaphragm lifts the needle quicker, and that would give me a more immediate response from the carby, but to make sure it doesnt run too rich too quickly. I might look into that because a snappy response would be fantastic rather than all out speed
     
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  2. geesex66

    geesex66 Active Member

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    Yes as I mentioned before, a previous owner had completely replaced the exhaust and silencer. Instead of two separate exhausts I have two into one on the right hand side, and a silencer with brand "formula1". See photo below

    As for how it was running: It was reliable, but sounded like crap, and was low on power

    IMG_3060.jpg
     
  3. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    Will be interesting to see how Bens bike goes with that mad looking 2 into 1 system and some jetting games.

    I intend to have some form of the same thing .... for the looks but also hopefully a bit of performance as well.

    I presume now you will have to fit new filters as your airbox is in pieces? :D
     
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  4. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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  5. Ben Mulligan

    Ben Mulligan Well-Known Member Premium Member Contributing Member

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  6. geesex66

    geesex66 Active Member

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    Yeah I'm doing somethig similar. I'm going to keep the pipes and wrap them, and I have a chromed straight through 'silencer' to replace the current one.

    And yes I bought some pods, they look the same as the ones Dave H has. The airbox pieces are making quite handy storage pots for the engine bolts :D
     
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  7. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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  8. geesex66

    geesex66 Active Member

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    OK so back to the tuning. My bike now has pods instead of an airbox, and a straight through silencer (that doesn't do much silencing). I think its the same as this one:

    http://www.ebay.com.au/itm/Black-Sh..._Parts_Accessories&hash=item233857c1a5&_uhb=1

    The exhaust was non standard anyway. At some stage a previous owner created a two into one pipe that comes out on the right side. I just changed the silencer. And wrapped the pipes with tape to cover the rust :D

    The first thing I had to do to get the idling right was to turn the pilot screws way down to a quarter turn out. That made a big difference, now its starts much easier. Will need further adjustment I'm sure.

    With report further tuning progress as it happens
     
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  9. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    That sounds like great progress mate ..... thats the header and muffler set up I was going to do possibly.

    Ill be really interested in how it goes :thumb_ups:
     
  10. geesex66

    geesex66 Active Member

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  11. VonC

    VonC Active Member

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    Just joined 2fifty,
    Have a 81 gsx250 build i'm currently toying with the jets.
    PO had a 2-1 exhaust made up and a Reverse Cone 'silencer' popped on. I've got Pods on it too and just want to see how other peoples jetting sizes worked out.
    I bought a jet-kit off the net the other week, but it came with MJ's 122.5, 127.5, 132.5.
    Thought they might be a touch too big seeing my stock MJ is a 117.5.

    Any thoughts or updates?
     
  12. Murdo

    Murdo The Good Doctor Staff Member Contributing Member Ride and Events Crew

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    Fit the 122.5 and try it.
    Only way to know for certain will be on a dyno, so expect to spend some dollars to get it right.
     
  13. VonC

    VonC Active Member

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    Yeah ill just have to experiment I guess. I'm not super keen to spend all that cash that a dyno will cost.
     
  14. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    Welcome mate

    My GSX is certainly a long way from running and sadly there hasn't been much update lately from the other lads with them ..... maybe they all have them running sweet and are out riding :)

    Would certainly be interested in your trial and error results. :thumb_ups:
     
  15. VonC

    VonC Active Member

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    Well I've got the 127.5 MJ in and the pilot jet that are with the kit too (can't for the life of me remember the number.
    Kit info http://m.ebay.com/itm/330590782868?cmd=VIDESC
    There's a bit of a flat spot taking off in first and I think I need to balance my carbs again. The idle is a bit up and down.
    I was going to try make one of the DIY hose and bottle carbys sync units. But I can't find where to attach them on the BS30SS. Has anyone done this on theirs?
     
  16. Ben Mulligan

    Ben Mulligan Well-Known Member Premium Member Contributing Member

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    Wait? You screwed them all the way in, then only a quarter turn out? So that lets in less fuel or less air?
     
  17. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

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    Bigger jets does not equal more performance. More fuel but the same amount of air = running rich. Use the standard jet sizes.
     
  18. Ben Mulligan

    Ben Mulligan Well-Known Member Premium Member Contributing Member

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    I dont care about performance at the moment mate I want the bike to run without my choke out.
     
  19. Spudley

    Spudley Member

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    Hey everyone, I've just put a deposit on my new little run about while my other bike gets a rebuild.
    I haven't gotten it home yet, but it's an 1983 GSX250 that's had a few mods done, including pods, 122.5 main jet and a 2-1 exhaust.
    On the test ride it felt like it was running out of power on wide open throttle, so I'm guessing it's got a main jet that's flooding the carby? Anyone have any suggestions, or should I just return it to the stock main jet and see how it runs?

    [​IMG]
     
  20. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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