Furbird Posted February 22, 2009 Share Posted February 22, 2009 Where to begin. First of all, this is on the dragbike, which has had at least 2 previous owners, been crashed, beat to hell and back, and now has parts off of probably 5 bikes to get it even close to acceptable for racing purposes. My problem is with the brakes though, so we'll narrow it to that. This bike had been delinked in the most assinine way I'd ever seen. Factory rear caliper and master cylinder setup, but the lines were two of almost identical length bolted directly to the master cylinder with a double length bolt, one going to the port that feeds piston 1 and three, and the second to the middle port. It works, doesn't leak, and bleeds out fine. So the rear is removed from this discussion. The front on the other hand was all kinds of screwed up. It only had a right side caliper on it and the main line from the master cylinder was about 3 inches too short, but that was ok for them because they had just lowered the forks in the triple tree 3 inches to make up for it. It was hell getting it on the trailer when I bought it, and that turned out to be the culprit. The main line dropped down to the port that feeds the first and third pistons. A shorter hose, approximately 4 inches in length was daisy chained from that line through another of those double length bolts to the second piston in the middle. There was no left side brake at all. Fortunately, I had a complete braking system off of a bird that I had gotten some time back that's been sitting on the shelf. I fabbed up a delinking bracket and used the original brake hose setup from the factory bird lines that has the two hard lines that drop down each fork leg to the calipers. The feed hose is plenty long to reach the master cylinder, so I assumed that it is the original line that actually feeds the front calipers on a factory bird. So at this point, I have all three pistons on the right side caliper fed with fluid, but only two on the left side caliper (the main ones, middle port is left open which is not a problem because it is still separated from the other two). I spent probably two hours the old school way trying to bleed the front, and the bitch just will not bleed. I can get pressure, and it locks the wheel up, but the lever is almost touching the grip. I went to Harbor Freight today and bought one of the Mityvac bleeders and spent another hour on it, making sure I got nothing but fluid out and it is all new fluid. It made it slightly (we're talking less than a 1/4 inch difference here) better, but it is nowhere near my still-linked setup on my street bird. You guys got any ideas? I'm thinking about pulling that daisy-chained hose off the right side caliper and just using the two main pistons on that side so that it replicates what I have on the left side. No fluid seeps out of the middle piston on the left side (remember I left that open) so it won't be of any concern. Short of that, I'm thinking I may have to rebuild or replace the master cylinder, because I really can't think of anything else to do. Is there some adjustment on it that I am not aware of (other than the lever adjustment, which is maxed out)? Suggestions? Quote Link to comment Share on other sites More sharing options...
cbrxxquad Posted February 22, 2009 Share Posted February 22, 2009 quick read impression, only, not to really answer like I have comletely understand what you said. Does the line that goes over to the left side loop over might have air traped in the top. Can take the caliper off and hold up so the air can get to the caliper bleed and out. Might be completely off base. Sorry if it is. Trying to help. Quote Link to comment Share on other sites More sharing options...
Furbird Posted February 22, 2009 Author Share Posted February 22, 2009 I don't think it's bent that far, but I will check that when I go back out again to fight with it. Quote Link to comment Share on other sites More sharing options...
rockmeupto125 Posted February 22, 2009 Share Posted February 22, 2009 If you don't have a good seal with the crush washers between each component on those double length bolts, its possible for them to suck air. BUT...you say you're getting a good lever and strong braking....just too close to the grip. Do what you thought...take the right center piston out of the circuit. You're trying to push 5 pistons with a system designed to push 4. Its doing it, but because it takes 25% more fluid (mabye 20%, because the center cylinder is smaller, I believe), the lever needs to travel farther, and ends up close to the grip. Stock grab is with 4 pistons...that should be more than adequate for hauling the bike down from dragstrip speeds as long as you have some quick-bite pads like EBC's. The system on the bike as you got it probably worked nicely, as it was only pushing 3 pots instead of 4. Quote Link to comment Share on other sites More sharing options...
Furbird Posted February 22, 2009 Author Share Posted February 22, 2009 Removing that line took care of it. There were no leaks, just too many pistons. Now that you guys mention that, it makes sense why the rear grabs so hard, as it was designed to push 4 but is now pushing 3 and with far less line than before. On the single caliper thing, let me tell you, that royally sucked. I rode it up and down the street a couple of times and it was like it didn't have a front brake at all. It may have been bled incorrectly or a locked up piston, but the rotor was completely shot so I know that wasn't helping. The first time I took it to the track I had the old rotor off my streetbike on it to eliminate that issue and had put new fluid in it, but it still sucked monkey nuts. I think it's been that looped line the entire time. Unfortunately, now that the front brakes work it exposed that the steering stem bearings are SUPER loose, so now I get to pull the triple trees down and fix that. Fine by me, better to figure that out at home instead of at 120 through the traps. Quote Link to comment Share on other sites More sharing options...
jon haney Posted February 23, 2009 Share Posted February 23, 2009 Removing that line took care of it. There were no leaks, just too many pistons. Now that you guys mention that, it makes sense why the rear grabs so hard, as it was designed to push 4 but is now pushing 3 and with far less line than before. On the single caliper thing, let me tell you, that royally sucked. I rode it up and down the street a couple of times and it was like it didn't have a front brake at all. It may have been bled incorrectly or a locked up piston, but the rotor was completely shot so I know that wasn't helping. The first time I took it to the track I had the old rotor off my streetbike on it to eliminate that issue and had put new fluid in it, but it still sucked monkey nuts. I think it's been that looped line the entire time. Unfortunately, now that the front brakes work it exposed that the steering stem bearings are SUPER loose, so now I get to pull the triple trees down and fix that. Fine by me, better to figure that out at home instead of at 120 through the traps. I tried the single caliper also on my dragbike and had the same opinion you have. It sucked. Went back to four pistons, and it's fine. Once I even locked the front wheel briefly at 135 MPH. Luckily, I got off the lever in time to save it. Word of advice for bracket racing: If you think your going too fast at the end, USE THE REAR BRAKE ONLY. Quote Link to comment Share on other sites More sharing options...
rockmeupto125 Posted February 23, 2009 Share Posted February 23, 2009 What sucks about brakes that will lock the front at 135? Too touchy to modulate properly? Rear brake, huh? You guys out there have different runoffs than we have in the east. Quote Link to comment Share on other sites More sharing options...
cbrxxquad Posted February 23, 2009 Share Posted February 23, 2009 Slick for what ever reason sucks and the front is just to important to be sliding, so just to have habits that help, I have the practice to always get on the rear first and then the front. When on a bike. But, also on the quad. More to set and align, even if the front slips it is like a chute to point the bike corectly. This practice saved me a year ago, in Gruen, Texas downtown, an old historical town with well wore cold streets on my zxxx and the pr2's at maybe 10mph preparing to stop in traffic for a red light. Front slide from normal braking about two feet. Some streets and surfaces even clean are not made for traction. Had it happen in another town at Daxx meet last year. That is what got me in 94 on my VFR and started the practice. But that was oil and faster. Quote Link to comment Share on other sites More sharing options...
jon haney Posted February 23, 2009 Share Posted February 23, 2009 What sucks about brakes that will lock the front at 135? Too touchy to modulate properly? Rear brake, huh? You guys out there have different runoffs than we have in the east. After I cross the finish line, I still use the front brake to slow down, but I apply it gently. The problem I have is no "brake feel" or feed-back with the front end strapped down. I didn't even know I had locked the front wheel until the bike started leaning to the left. Quote Link to comment Share on other sites More sharing options...
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