Based on this previous question I found out that this frame can actually support V brakes and that I had to change the levers to a specific V-brake lever type. I bought some V brake levers, but they cannot be easily fit into the handlebars.
The diameter of the whole is fine, it's just that I cannot fit the lever in because it needs to spread, but I cannot spread it wide enough.
I tried with a screwdriver, but it actually ended up breaking. I tried to take out the grip on the handlebar but it's glued.
Did I get the wrong levers for my bike? Are there some levers more flexible to be able to force them into the bars? Is there any other technique? I've found some that have a hinge, but they are not for V brakes.
The pic shows the lever that's not broken, you can see the handlebar on the background.