I need help tuning / syncing my carbs!
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Bike Model = : GT125R 2016
Hello, I’m a beginner bike mechanic and am wondering how to perfectly tune my bike without any of those compression reader tools and etcetera. I have installed a 17.5 pilot jet in both carbs as I have an open exhaust and performance airbox. My front carb’s mixture screw is set to 3 turns out and my rear is set to 3.5 turns out. My float height is 7mm, I have the bike’s idle adjustment set to 2k rpm because when i drop it to 1.5k it just doesn’t feel as responsive of the bat. I have been fiddling with a screw at the very bottom of the carb which I believe is the sync screw. I have tried to replicate online but my bike makes an uneven beat now and I haven’t been able to find a reliable and clear audio of a GT125R with an open exhaust idling so I can hear what the pattern is suppose to sound like. If anyone has any tips, or audio of a GT125R idling so I can hear the pattern it’s suppose to make that would be very appreciated. Thanks!
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They never ran well with 17.5 pilots , so you will want to downsize back to 15 each pilot. Use 2.5 turns out as a base then see how it responds.
You may want a baffle in the exhaust as i have not experienced a 125cc in the past that run better without baffles.And is it still having its original airbox on ? without it you will have hell , a lot of us tried to do away with the stock airbox but the engine & carbs wasn’t having it even the 650 sister.
The middle screw of the carb isn’t usually touched once set by the factory, you want both butterflies to open at the same time but with a little bit more air to the rear (since it uses a bigger jet)
You did not say what the main jets are so i could not comment further
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With the size 15 pilot jets in I was having to turn the mixture screws about 4 to 4.5 turns out (almost coming undone) just for it not to feel laggy and when I re-engage the throttle after letting it decel down while riding in a gear it can bog out for a second or two before restoring power. With the 17.5 pilot jets in I have been having much easier cold starts, and less problems with the bogging out but it’s still their just very slightly. My main jets and everything else are still the same. Yes the stock airbox is on the bike but a better air filter is in the airbox.
As to your very first point, the bike seems to be happier with these 17.5 screws in, I just need help with fine tuning and the sync screw at the bottom has been changed by someone else who had the carb and I think it’s been set wrong. From my knowledge, turning that screw will move the plate on one of the carb butterflies. I could be wrong but thats what I know of right now. I just want to see if anyone has a video and or audio file of a Hyosung GT125R 2016 idling so I can hear the correct exhaust beat pattern and change the sync and idle adjustment so it is better.
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