Here's the situation. My RZ has Suzuki 4 piston calipers up front and a Nissin brake cylinder with remote reservoir from I think a Honda CBR 900 or F3. When I bought the bike last fall, the lever travel was much more than I was used to. The bike still stopped well, but the lever feel did not have a nice short, firm travel. I thought, old fluid and maybe some air in the lines. So, I bled the brakes - a lot. Still, the lever did not change. I raced the bike at RRR on 3/23 with this condition. Again, the bike stopped well, but the lever travel was too much and not to my liking. I have decided I cannot live with this condition. I grew up racing motocross and am used to braking with my middle finger only (yea, I know, bad habit). With good, firm brakes you can do this. With my brakes, my other fingers get in the way so I have to lift them off the grip. Anyone have an idea on how to fix this?
In addition, brake pads are like new, rotors are in excellent condition, and stainless steel braided lines are installed.
Vintage Brake has a mastercylinder to caliper ratio chart. I could scan this to help you get the right mastercylinder to caliper piston ratio and e-mail it to you if I can get your e-mail address. Eric
Does the lever feel spongy or does it have a lot of initial travel and then firm??? It is nearly impossible to bleed the brakes the conventional way. I pump the fluid in from the bottom using an oil squirt can and some clear hose. Try this and see if you get some bubbles out of the master cyl. Since the master cyl came from a bike with dual disc you should be in the ball park on the bore size. A smaller bore MC would supply a lighter feel but longer travel and vice-versa. Ray
It has long initial travel and it feels too soft compared to any modern sportbike front brake. Since my components aren't that old, I expect better performance.
You may have to remove the MC from the clip on and hold it at an angle so the the feed hole is the highest point and then bleed it from the bottom. With the MC angled up like this you can often barely bump the brake lever and burp some air out of the MC. Ray
Why not just go to: http://www.vintagebrake.com/mastercylinder.htm To bleed the brakes you really don't need any special tools or procedures such as vacuum bleeding or pressure feeding from the bottom up. Just make sure you have good brake lines, preferably steel braided and as RB stated, make the purge hole the highest point in the system so that air bubbles can escape. What also helps is vibration which breaks the air bubbles free from the lines walls and allows them to rise to the top. I just start my XS650 and let it idle for a while... on my street bikes I have always used an orbital sander (without a sanding pad) and touched it to the caliper and hose while pumping the brake lever. Majik I tell ya!! Heed the advice from Mercury's ratio chart. My XS650 had a stock 13mm piston MC and the lever barely had about 1/2 inch of travel out of about 4". I moved to an 11mm MC and the brakes can be applied using only two fingers and offer great feedback. I also have Ferodo Platinum pads which are fantastic! [This message has been edited by Diesel (edited 04-22-2002).]
Ye hawwww! I just got home from vacation today and a box from LP USA was waiting on my door step. Inside was a new master cylinder with 5/8 in. (approx 15.8 mm) piston diameter. Well, I couldn't wait to install it so on it went after making a reservoir mount. That cured my problem. I now have a nice firm lever feel with shorter travel. Hopefully, it will feel just as good on the track. Thanks everybody for the advice, especially Mark M.
