2007 GT250R – carb help [Solved]
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Bike Model = : GT250R 2007
Hey all I have recently picked up a 2007 gt250r With only 2000km on it and am having a bit of trouble with it. When I received it it would run but would die off on idle and was lazy on the throttle and rev by itself. What I’ve done so far is replace fuel/vacuum lines, spark plugs, fuel filter, petcock and rebuilt and rejetted the carbs to the bigger recommended jets. The trouble I’m having at the moment is now it won’t start at all and I’m at a bit of a loss, I was just wondering if anyone had any ideas or tips for me to try before I try and find a mechanic locally. I will also mention that I have known the history of the bike since it was brand new and the fuel mixture screws have not been touched by anyone as that was a worry of mine.
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Did you change the Pilot Jets ? (if yes they should stay at Size 20 forever) and is the airbox ON ? They don’t really like to run without the OEM airbox attached to it.
(Weird upside down CV carb physics)It sounds silly to say this but have you checked the sparks on both cylinders?
Also, remove the intake pipes going to the cylinders and check their o-rings. Just even a tiniest leak from there runs the whole bike as they are very fussy when it comes to that , its easy to lose vacuum without realizing it. The previous owner may not have touched them since it was new, but enough heat cycles over the years will necessitate the replacement of those O-Rings.
Find something like this exactly:
Spray the inside the AIR FILTER CATRIDGE or the AIRBOX INSIDE = About 3 seconds worth of spraying. Then fit everything back in nicely including the tank.
Do this outside the garage if possible as this stuff can light up in flames if anyone is smoking near you or weird sparks happening from electric sockets in garage, etc…. I can’t stress this enough.
Put the bike on Full Choke. Start it and let it scream for 2 mins on choke, make sure it has fresh new fuel.
Slowly wind down the choke lever and adjust the Idle Screw Tickover at the same time until it revs around 1500 rpm cold (it will rise to 1800 max when its hot which is maximum recommended) although Hyosung says 1500 max all day , i find 1800-1700 sweet enough. Don’t exceed 1800 rpm as you will be very slowly cooking pistons idling in hot traffic.
See if these tips helped ?
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I ended up getting it to kick over using a bit of spray in the air box but it would rev up to around 6k and come down to about 4K and stay there whilst piping and banging. I didn’t change the pilot jets only the main jets. I will hopefully get a chance to take a look at those o rings this weekend but I should also mention it has an upgraded air filter, muffler and the recommended bigger jets which I think from memory was a 95 and 97.5.
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As long as it has the original AirBox on it, the K&N catridge + updated mains should be fine. Main Jets only activate fully when on the road.
If in the garage / stand still traffic, its your pilot jets that do the work. See what happens when you do a deeper dive over the weekend.
Good luck!
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ok so I changed the pilot jets last night and put it ack together this morning. I also checked those O-rings and they are fine. she idles and starts fine now but now it has a new problem. once I got to about 4k it feels like it bogs and struggles to climb in the rpm, low down it feels fine just when i try and get on it
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it could be possible you have sticky slides that wont go above a certain RPM
Have you tried this mod below?
[How to Tutorial] Adjust Carb Slide Needle (Tuning) Hyosung GV250 GV125 GT GT125R GT250R
Least you want to investigate the needles are also not getting jammed inside the Needle_JET tube (brass) , as the more revs you need, the higher the slide must lift for air passage and fuel to leave the main jets.
Not unless the the skeleton of the carb itself , needs compressed air (again yes)
This is the closest video that explains what part of the carb is activated and gives you more pointers to look for
(Video is only viewable on youtube, due to the uploader making it that way)
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happy to say she is running amazing now! i adjusted the needles and also set the float heights and gave the jets another good clean and she runs amazing now. thankyou so much for your help and words of wisdom i really appreciate it
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