I have the GT125R-2017, bought new a year ago, as new overlayer(3+ years!!) Went thru the run-in-process last summer, then fitted :
BlackWidow system; pipes & muffler,(loud, even with largest can); https://www.blackwidowexhausts.co.uk/hyosung-gt125r-gt125-comet-full-exhaust-system-400mm-round-silencer-1295-p.asp
+ re-jetted with 6SigmaJet kit; https://www.6sigmajetkit.com/hyosung-gt-125-r-s-comet-jet-kit.html
– now with the largest jets: F-95/R-97,5. (Bowl-Level checked ok, dry, and wet). Still running lean…????
Sparkplugs are still as white as new.
I can get a GPS controlled 70+mph (with ”520-upgrade” DID-VX3 & JT-13/46t) = good enough, but there are no power/torque at top-end, (feels lean), drops speed (and rpm) as soon as you can see the road rise upphill, or god forbid, I meet wind…
Bike is ”almost new”, just round 500 miles total, (have changed oil/filter 4 times, (more than needed), but the almost black oil I emptied out after the first 50 miles scared me…been better thereafter).
Shinko-Tires swapped to Bridgestone T32 front & Michelin Road 5 rear.(stock size).
(Tried NGK Iridium Spark Plugs; DCR8EIX – no change)
Back to question: Lean? Not enough fuel supply? Or should I just try even larger jets?
-any/all spelling-mistakes are dedicated to my teachers…I’m Norwegian…
BTW, had a 2014 Honda Varadero XL125V -3 years ago, similar weight, had more power, (watercooled & injected), but no stability compared to the Hyo…