Hey guys, as you may or may not know, I am rebuilding my F4i. I bought it as a stunt bike and slowly but surely I am fixing all of the little problems that I inherited along with it. . Anyway, I have had the bike for almost two months now and I have ridden it at least a couple times a day. My main concern now however are the brakes. Approximately 5 days ago after a half hour ride on the highway I got home parked the bike and went to sleep. I came out to the bike the next day and found that the front brakes were locked on the bike. The front lever felt very solid with only about a half inch of play. I was thrown off by this as maybe 4 days ago I had flushed and vacuum bled the brakes and had never before had any trouble with them before or after doing so. (I just flushed the fluid as routine maintenance.) So I took the stock (not aftermarket) lever off as I though hell maybe I could adjust something and I rotated the adjustment wheel a little, put the lever back on and somehow, the issue had gone away. So I thought nothing of it. I rode to the bank about 15 minutes with light traffic and after returning from the bank to the bike I tried to back it up only to notice that it was definitely hard to move the bike backwards. I overcame it, but then going 70 down the road I downshift to slow down and cruise but need to speed up to avoid a stupid driver however, when I try to speed up, the bike lacks power. I thought my clutch was officially wasted and was slipping like crazy cause I gunned the throttle expecting a response and barely got anything but then I come to a stop to find out that the damn brakes are locked!!! Long story short, I have checked the calipers and there are no stuck pistons they work perfectly well. I have also replaced the master cylinder with a used OEM which was verified to work (by me) on the last bike that it was on to no avail. I did notice that the stock lever usually stays applying slight pressure keeping the plunger maybe 1.5mm back and that sometimes when the calipers drag a little on the rotors if I lift the lever to make no contact with the plunger, then I will no longer feel resistance moving the bike. I also feel that when I really squeeze the brake lever down it starts building more and more resistance while I stay applying the same amount of resistance and eventually starts pushing the brake lever back up to what is supposed to be "disengaged brakes position." I say this half sure/half maybe crazy as this issue has me all over the place and hell maybe I'm imagining that lifting the lever actually helps. I checked the little relief hole on the MC next to the large reservoir feed hole and I can see that when I fully extend the lever back and forth, the small relief port does spew out a stream of brake fluid. WHAT THE HELL COULD BE WRONG!!?!?! I appreciate any help guys and girls thanks a lot in advance!

 

Sounds like a problem with the master cylinders as you say the caliper pistons move in and out ok? Try dismantling them, cleaning them with clean brake fluid and renewing the pistons and seals. Also make sure you have enough clearances in the brake levers. Keep us informed as to how things progress?

 

The issue is only with the front so it would only be the front master however, I replaced the master and saw that it definitely worked on the last bike it was on so I wonder what could be causing it to mess up on my bike? I bled the brakes but is there any possibility that somehow a ridiculous amount of water got into the system over time (although while bleeding the fluid came out brown at first and then came out very nice and clear on both calipers) and that the water is expanding and causing the brakes to lock? Also has anyone ever had this issue with stock levers? I know plenty of people had this problem with aftermarket ebay levers but never read about anyone having an issue with stock levers. Can anyone check their stock lever to see if their stock lever pushes against the plunger slightly or if the spring loaded plunger is supposed to push the end of the lever out to the point that the plunger is 100% out when releasing the brakes? I appreciate the help guys I could really use it as this bike is my DD and I need it running safely ASAP.

 

the system only has 3 parts; master, lines, and calipers. since the master is "new" and calipers are good, be looking at the brake hoses. the can collapse internally, causing them to not release pressure. that is assuming that the master is not being applied, and the calipers are in good working order.

note: i had a shop put on a front tire for me a while back. when i left, the brake felt spongy and the front calipers were locked up. turns out that the spacers were "put in wrong, or mixed up." i do my own tires now, but maybe something there if you had your wheel off.

 

I suppose the idea of a collapsed line is a possibility although they are goodridge lines but they are older so that may be it. However the whole spacer thing has brought up a concern. I just looked at my front wheel and noticed that the tire was mounted incorrectly. The tire is rotating the right way however the wheel is on backwards. My question though is that I had no problem for 3 days of riding hours and hours after I got the new tires on and that it took a while for it to actually start happening. Have you heard of the wheel being backwards and causing the brakes to lock or should I start pricing out a replacement to my goodridge stainless lines? Thanks again for the help!

 

Sorry the rotors are rotating in the wrong direction (My previous post was based off of the directional arrows on the right front rotor) I'm not sure if the wheel is also I'll check that out too.



EDIT: Hey guys, I just checked and the wheel is in the right direction it looks like the previous owner just installed the rotors the wrong way. Still trying to figure out if its anything but the brake lines since I don't want to have to pull the trigger on new lines.