Help，t120 Black Edition Shakes Really Bad

Hey everyone, I’m new here—glad to join the community! I picked up a T120 last year (2024) and man, it was such a joy to ride at first. But only after 600 km, it started acting up. When I twist the throttle quickly at low RPMs, the bike shakes really bad.

I made a video to show the difference: the first half is how it should run, smooth and normal. The second half? Total night and day—even at almost the same speed and RPM, the ride gets super rough, it’s really frustrating.

Worse yet, I took it to the dealer, they checked it out and said “nothing’s wrong with it.” I’m stuck here, so I figured I’d ask you guys: has anyone else had this issue? Or does anyone have tips on how to fix it? Would really appreciate any help!

 

Thx Joe

Thanks a ton, Joe! Really appreciate you walking me through this—super helpful. I’m gonna hit up the dealer this weekend and have ’em check things out like you suggested.

Quick add-ons to fill you in: This T120’s brand new, but I messed with the exhaust a couple times before the issue popped up. First, I just swapped the tail section for a Motone Jupiter cover. Then later, I went all in—yanked the cat, cut the whole exhaust, and threw on a shorty. But honestly? The low-end torque was garbage after that, so I switched everything back to stock. Oh, and I also chopped the rear fender to make it a bobber style too.

Do you think any of these mods could’ve messed something up and caused the current problem?

 

Hey Johnjo!
Super stoked to get your tips. I tried the method you mentioned—my dealer even helped reset the engine—but the shaking still hasn’t gotten better, unfortunately.

 

thanks Kinjane，I first noticed this fault back in November last year. My dealer mentioned it might be water in the fuel tank, but they never fixed the issue. Since then, I've put roughly 2,000 km on the bike over the past year. Could the water in the tank still be lingering and causing this problem?

 

Thanks a lot Taran! I totally get where you’re coming from with this bike. First and second gear do have that jerky feel, but my issue is more with the vibration. Did you happen to notice the difference between the first half and the second half of my video? Normally, the engine responds super smoothly to the throttle with steady acceleration, but now, when I twist the throttle, there’s this obvious "da-da-da-da" sound and a lag in speed. It’s been really frustrating for a whole year now.

 

Hi，Pegscraper,Thanks for your analysis and tips! The dealer already helped me replace the spark plugs, all the exhaust gasket seals, checked the data from every sensor, and even swapped out the clutch friction plates—but the issue’s still stubbornly hanging around. How do I check for a cylinder misfire myself? Or how can I remind the dealer to look into this possibility? Would really appreciate more of your advice. Thanks again!

 

I just got back from the check-up. The dealer said the tires, swingarm, chain, and brake discs—everything checks out. Seems like the only one with a "problem" here is me, for being so particular...

 

Folks, I’m back again! This weekend, I headed to the dealer once more for all sorts of checks—and surprise, surprise, the results were “all normal” yet again. But this time, I propped the motorcycle up on its stand, pressed the rear brake slightly to give the bike some resistance (to simulate the starting process), and I made a new observation!

When I slowly released the clutch, the tire started spinning, and everything felt fine at first. But the second I let the clutch fully engage? The bike started shaking. I’ll upload a video showing this whole process—even though the issue might not look super obvious on camera, you can still catch it if you pay attention.

Anyone here able to tell me if this is normal? At this point, I’m even wondering if I’m just being too sensitive… but one thing I’m sure of is that none of the other bikes at the dealer have this problem.
the youtube video link https://youtube.com/shorts/K8tCYnE37KQ?si=wD7x2zoNg8ELr2B6