[BananaBreadF4i]

So this is going to sound dumb, I’ve had a black 2017 for almost a year now (1800 miles). Just picked up a silver 2017 ( a little over 5k miles) with some simple aftermarket parts on it, exhaust, 12 bar/ cosmetic stunt parts. The issue is, first off the clutch was completely toasted. Replaced it and adjusted it no problem. compared to the low mile black one it seems to struggle getting the front wheel up and to balance point and just feels like I’m fighting the bike whereas my original black 17 I can comfortably get to BP with almost zero effort. I am completely mind boggled. The twist throttle feels like it’s been replaced with one that has almost half the travel (twist). The 2 are set up almost EXACTLY the same aside from the exhausts but 1 is smooth on all levels. And the other shifts hard, and wants to fight with me on everything. I’ve had the cases open, checking for any missing teeth or any visual problems. Nothing at all.

 

[BananaBreadF4i]

Completely forgot to mention! Previous owner stated that he only got the loss of power/fighting feeling when he went from a 120 height tire to a 140. Went back down to a 120 and it feels the exact same. (GREEN grips is the problem child)

 

[BananaBreadF4i]

 

[Azlar49]

Are the sprockets the same across bikes?

 

[Kaw'ee]

Gear ratio changes from taller tires or sprocket changes as Azlar49 mentioned would be the biggest noticeable issue.
The 120/xx tire you put on is probably taller than the stock tire height. Therefore did change the gear ratio

The black model is a 2018 but no difference, both bikes are the same except color of plastics

Second would be engine HP performance.
Do both bikes hit the rev limiter in 4th gear
If both do, put a passenger on the back and test it again to see if one bike does have less performance than the other.

If the gear ratio is the same and performance is the same, start switching the different parts from bike to bike

Rear tire
Quick throttle.
Exhaust.
And even the bike's ergonomics can make a difference if the handlebars height and tilt are different .

The shifting issue is best improved when using a full-synthetic engine oil and everything listed on below chart