Bike only runs on one cylinder once moving – 2009 gt250 carby
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Bike Model = : 2009 gt250 carby
hi all, I have a 2009 hyosung gt250 comet I bought as a project for myself, when I bought it didn’t run or drive at all. Well after replacing the plugs, coils, all fuel and vacuum lines and cleaning all the jets I got the bike to idle strong. My problem happens whenever I start to move only the rear cylinder fires and the bike will only go 40ish at wot. I also changed the jet size it 95 front and 97.5 rear and deleted the fake egr, however it had the same issue before this. All help is appreciated!
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Does it accelerate OK at 1st to 3rd gear ? and what RPM is 30mph ?
Grab a fresh set of CR8E , fit them in and ride for a short distance, come back, let it cool down, take the plugs out , take a few pictures and upload them here, so we can see what’s going on?
Either we have a fueling problem or the HT Caps (not coils) are waning or the carbs themselves need attention.As it’s idling, spray carb cleaner on the rubber intake pipes and find out if the revs change ? (It could be a good idea to change the O-RINGS under the intake pipes as if they are caked up dry , old etc, they will cause all kinds of weird issues when the vacuum system is not sealed tight.
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First one is the front cylinder, second is the rear, these are 4303 not CR8E as my local parts store were out of stock. Like with approximately 5 miles. The bike only accelerates kinda decent in first, after shifting out of first a pedal bike accelerates faster, when spraying around the carb when I sprayed between the carb and intake box on the rear cylinder it killed the bike, not sure what that indicates. Haven’t checked the seals on the bottom of the intake boots yet -
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You should replace those suspicious plugs with CR8E if that was what the previous owner did , then stay on CR8E forever as it’s the OEM plug , don’t fit “IX Iridiums” as they don’t like them for too long (Stock or LASER CR8E is best)
See what happens then, also if it dies when spraying the rear, you have a small air leak, the metal throttle bodies have 3x orings per cylinder (3x front and 3x rear), so if you get time, I would recommend stripping the intake system down so you can get to those O Rings, even old o rings can cake up due to old age rubber (it’s like having 20yr old tyres on the bike, you will start to see expansion cracks everywhere.
We should have a happy bike after this , as its only 2,000 miles old. So i am not expecting any electrical issues at this point but worth checking , and if you see anything oxidized like “rusty connectors”, just give them a clean with contact cleaner.
When it comes to the ECU = Do not spray any liquids, always use dry compressed air on the ECU socket plug, it will thank you. Clean electrics should translate to a snappier bike overall
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