Ill try to keep this short. I was never into stunting big bikes, so I never became familiar with particular parts, like a rear hand brake set up.

So I came across this 01 f4i completely stunted out (very used for what it was meant for) for very cheap so I couldn't pass it up.

I rode the bike like normal for a few weeks, and i noticed that when I pull the rear brake, the first initial pull will be a little squishy, then after that its nice and firm. I didnt think anything of it.

So I decided to finally try to stunt it. After about 30 minutes of practicing, i completely lose pressure in the brake and loop it. I didnt use the brake at all until i got home and it was back to normal.

Well today i took it out again. And again, after about 30 minutes, the brake will lose pressure until i pump it about 4-5 times and it will be useable. until i attempt my next wheelie.

I'm not familiar with what kind of setup this is, so I dont even know where to start to look into replacing parts. I can tell by the hose clamp on the master cylinder that the setup might be kind of ghetto? Anyone have any idea whats going on??

 

2nd time stunting a big bike

 

Maybe try going to a steel braided line. Make sure fluids and all the obvious are good as well.

 

first be positive there are no leaks and no air in the system. a lot of times a problem can be found by doing leak checks. if the problem is still there then you probably just need to rebuild the master cylinder. when the seals and piston get hot/warn out, fluid leaks past and no amount of bleeding will cure it.