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Thread: GSXR250 "issues"

  1. #1
    Join Date
    26th September 2014 - 17:29
    Bike
    2012 S1000RR
    Location
    Auckland
    Posts
    106

    eek GSXR250 "issues"

    Hi guys,

    (thankfully) long time no talk.

    I have a few old bikes kicking round in the garage Ive been trying to get working again or summer, one of those is a gsxr250 '89 which is frankly turning out to be a bit of a pain in the ass.

    I ended up buying a reposer engine/carbs kit for it as the original one was giving me grief, but I still cant get it working correctly.

    Typical symptoms are;

    - the faster you go the slower the bike wants to rev
    - if you do a full gear pull, the second you change into second (or any subsequent gear) you feel a huge drop in power and it seems unwilling to rev
    - generally just surges and runs like shit

    It does idle fine, starts up with no extra persuasion and will rev (relatively) cleanly when not under load (although even that sounds a bit strained tbh).

    What Ive tried;

    - swapping the carbs for my original pair
    - cleaning and blasting the carbs and jets
    - swapping all the best parts of the two sets of carbs
    - checking rubber diaphragms for cracks (none that I could see)
    - changing the little rubber o-rings for the mixture screws
    - visually balancing the carbs (don't have a balance kit but understand this shouldn't cause issues as described above anyway)
    - adjusting mixture screw in all directions
    - checking all vacuum hoses
    - running with the tank lid open
    - running with / without a filter
    - running through a tank with injector (fuel system) cleaner
    - changing plugs (including a grade hotter / colder then needed)
    - recutting leads
    - checking spark on all cylinders
    - feeling exhaust headers to see if they heat up evenly (they do so far as my handometer can tell)
    - trying a new battery
    - new fuel (been though a few tanks)

    Im feeling like maybe this is related to coils as I hear these bikes are notorious for electrical gremlins, can anyone comment on this?
    Would spark breaking down cause issues as described above? Specially what feels like a huge drop in power if I change up a gear / the faster I go..

  2. #2
    Join Date
    26th September 2014 - 17:29
    Bike
    2012 S1000RR
    Location
    Auckland
    Posts
    106
    On a related note, can anyone explain the difference between coils to me? Like can I just get a generic set of coils that I `know` works (like from a working ZXR400) and try those?

    On a related related note, can anyone thing of a good reasons not to buy a set of coils for this bike off Ali express? The bikes worth very little to me and if this would get it going that seems a worthwhile small investment (~$50 a set)...

  3. #3
    Join Date
    26th September 2014 - 17:29
    Bike
    2012 S1000RR
    Location
    Auckland
    Posts
    106
    Quote Originally Posted by imthatguy View Post
    On a related note, can anyone explain the difference between coils to me? Like can I just get a generic set of coils that I `know` works (like from a working ZXR400) and try those?

    On a related related note, can anyone thing of a good reasons not to buy a set of coils for this bike off Ali express? The bikes worth very little to me and if this would get it going that seems a worthwhile small investment (~$50 a set)...
    Actually I took it into work today and noticed that it wont even free rev when going motorway speeds, just seems extremely lacking in fuel / air.

    Is there some special step Im missing with the air box? its almost like the feeling you get when you try to run a CV carb with a pod filter..

  4. #4
    Join Date
    26th September 2014 - 17:29
    Bike
    2012 S1000RR
    Location
    Auckland
    Posts
    106
    Quote Originally Posted by imthatguy View Post
    Actually I took it into work today and noticed that it wont even free rev when going motorway speeds, just seems extremely lacking in fuel / air.

    Is there some special step Im missing with the air box? its almost like the feeling you get when you try to run a CV carb with a pod filter..
    Well, I worked it out almost by accident last night and for posterities sake Im going to leave the answer here because its so stupid it might catch someone else out.
    It turns out that the two hoses running from the middle site of the two carbs are in-fact breather cables (and / or fuel overflow hoses as I originally suspected), but they are extremely susceptible to external pressure.

    The way I had them leaving via the side of the bike meant that the faster I went the more wind was entering them which (presumably) was dropping the internal pressure differential within the carb, effectively making the bike run really REALLY lean. I rerouted them around the radiator overflow and through the rare shock space in the swing arm, and now the bike runs perfectly.

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