|This upgrade to the brake system was brought about due to that "squishy lever" feeling that's been building up on my '98; and since it only has one disc, I want it to work its best. I was due for a brake fluid change anyway so I decided to replace the stock nylon-braided rubber line with a much more dimensionally stable Russell stainless-braided line (part# 09386). The line is less prone to expansion under braking than the stock and should give a firmer feel in the lever. Since the system was being drained, I also added a Russell Speedbleeder (part# 40527) to the caliper - it has a built-in check valve to ease the bleeding process. The line came from Motorcycle Accessory Warehouse and the Speedbleeder from Dennis Kirk. Be sure to also have 2 (or more) pints of DOT4 brake fluid on hand for this process. This may be a good time to change brake pads if you're due, or to upgrade to pads with more bite.|
|PREFACE:||Tools needed include 8mm wrench, 12mm wrench, torque wrench, clear tubing, pliers, utility knife, bucket or jar for draining, Philips screwdriver, small squirt bottle or syringe, rags or absorbent pads, plumber's Teflon tape, patience.
You may want to also use a vacuum bleeder to assist in the initial bleed process. The bleeding took a lot longer than I imagined (damn air bubbles!) and I cycled through at least two pint bottles of brake fluid.
|REMOVAL:||Start by placing a bucket to catch draining fluid and placing rags to keep drippage off of any painted area (brake fluid eats paint). Over the gas tank, I placed a plastic bag and then a towel just to make sure nothing dripped through to the tank's paint finish. Then remove the master cylinder reservoir lid
and the bleeder
and allow the old fluid to drain. After draining, you can remove the banjo bolts that hold the line ends to the caliper and the master cylinder.
Discard the four crush washers (new ones come with the new line) but keep the banjo bolts to re-use. To remove the old line from the bike, you'll need to pry open the 3 mounting clips that retain the line to the bike.
|LINE/SPEDBLEEDER INSTALLATION:||First thing to do is clean the banjo bolts and the washer surfaces on the caliper & master cylinder so you don't have any crud affecting your washer seal. Also make sure you don't have any crud in the reservoir. Russell recommends that you "prime" the new line by filling it with new fluid -- use a squirt bottle or syringe to flow some fluid through the line. Attach the lower end of the new line to the caliper
(bolt-washer-line-washer-caliper) in the orientation shown and route the line through the brackets and up to the master cylinder. At this point, you may want to try to fill the line to make bleeding easier. Attach the line to the master cylinder
with its banjo bolt just like the caliper (bolt-washer-line-washer-reservoir)
and torque both banjos to 25 ft-lbs. Wrap the grommets around the line, place in the clips, and then squeeze the clips tight around the line/grommets.
|FILL/BLEED:||I found that it was easier to fill the line if I removed the bleeder and kept topping off the reservoir until the fluid started running out the bleeder hole. This was a quick way to work the fluid down the line and push some air out ahead of the fluid. I let it run through until I got a steady drip down the side of the caliper. Even after doing the pre-fill, it took forever to get all the air out of the line. Then I re-installed the bleeder and started the normal bleed process -- clear tubing on the bleeder to direct air filled fluid into a bucket, bleeder SLIGHTLY backed out, & start pumping the brake lever to force fluid/air out the valve. After a while, hopefully your valve excrement will be bubble free; but keep adding fluid to the reservoir and pumping for a while longer to make sure ALL of the air is out of the line & caliper. Once you're satisfied that the air is gone, tighten the bleeder valve lightly into its seat (only 5 ft-lbs I think). Top off the reservoir and replace its lid with the rubber bladder, the white plastic spacer, then the lid.
Some observations that I made: DON'T LET THE RESERVOIR RUN DOWN TOO LOW, don't loosen the bleeder valve very much (or air sneaks in around the threads), don't pump the brake lever too fast (about every 2 seconds worked for me), you can leave the reservoir lid off while you're pumping (fluid won't squirt up), have patience -- the results are worth the effort. You may want to also use a MityVAC (or similar) vacuum bleeder system to supply vacuum to the bleeder valve -- helps speed the process a little.
|RESULTS:||I was absolutely amazed at the results. The brake feel is MUCH firmer. I'm not sure if it's due to the new braided line, the new fluid, or the meticulous bleeding. Probably a combination of the three I would guess. I havn't ridden far on the upgrade yet, but the little I did ride indicated that the front brake is now much more controllable and easier to modulate. I also upgraded from the stock pads so hopefully I'll have more grab to go with this newfound lever feel.|
Dean of Ohio
1998 CB750 Nighthawk ("Midnighthawk")