What hoses are you using?
After finally sorting out my fuel leak-under-the-tank issues, I took the bike for the MOT ( an annual requirement here in UK ). Although the tester passed the bike, he did remark the front brakes were 'spongy', which I had to agree with. I think I'd just got used to them being a bit soft, the lever almost coming back to the 'bar with 'spirited' use.
Bought a master cylinder seal repair kit, as I'd replaced the caliper seals/dust boots in the recent past. Carefully fitted, and bled the system, but it appears no better than before. One thing that did seem odd was, after bleeding both calipers, and gently operating the lever, no more air was being discharged into the reservoir; however, when I squeezed the flexi-pipe between the reservoir and master cylinder piston chamber, air bubbles came out of the pipe into the reservoir. Must be the angle of the dangle, or something. However, this didn't improve matters by any great degree.
Since the bleed nipples on the calipers (standard tokico's) are pretty much at top dead centre, I'm wondering if there any other air collection points in the system causing my problem I'm not aware of. If you've an answer to this, please chime in!
Echoing Crash, if you haven't got braided lines, get some.
One thing you might try is to pump the pistons out a fair distance, (but not so far that they pop out), bleed then push the pistons back in as far as they will go. This should hopefully force any remaining air up out of the system. Need to have the cap on the reserviour loose so there's no resistance to the fluid flowing back up the lines.
Like my TL I'm old, overweight and badly maintained but I can still surprise you by how fast I can move.
Many thanks for the quick replies, fellas. My bike is a '97, and wears the four-pot Tokicos. At the moment, it's also got the original, standard brake hoses fitted. I was going to change these when I stripped the calipers and renewed the piston seals about a year ago (pistons removed, cleaned, and pushed all the way back in on reassembly). What put me off doing it is that I also have, amongst others, a '93 ZXR 750 L1, and changing these improved the braking, but lost a lot of 'feel' at the lever. Still like that about the brakes on the TL, but if it makes a big difference, I guess that's the way I'll have to go. In the meantime, I'll have a play around with pushing the pistons back in/out, and re-bleed. It also occurred to me that, if air is trapped in the link pipe from the L.H. side caliper to the double-banjo union on the R.H. side caliper. bleeding at either caliper wouldn't necessarily get this out.
Having thought about possible remedies for this, the only sure - fire solution I can think of, is to fill a syringe, plus a bit of attachment tube, with brake fluid, attach to the L.H. side caliper bleed nipple, open the nipple, crack the joint where the main brake hose meets the master cylinder, and pump the syringe to 'chase' any air bubbles out of the link pipe, and up the main brake hose, to be expelled at the slackened joint at the master cylinder (does that all make sense?). Messy, I know, but would this work?
First thing I would do is take the old brake lines off and chuck them in the bin. Replace them with good braided hoses, new crush washers and banjo bolts, bleed the system up again and you should notice a marked improvement.
The stock brake lines weren't anything special when they were new, and if you're are still original then they will likely have lost any structural rigidity that they previously had. When you squeeze the brake lever rather than the fluid pushing the pistons in the brake lines themselves are stretching.
To aid bleeding at the resevoir end I fitted a stainless banjo bolt with a bleed nipple in the end, cheep enough from ebay
open cap, flick the lever good few times, pinch/release the res tube (causes vacuum) , look for bubbles, vary the steering lock (caliper angle), keep on repeating. Used to have the same trouble, this will get the fine bubbles out it. takes 15 mins or so but only way I got to get it rock hard. (with braided)
Funny how everyone's so knowledgeable about everything since the internet was invented!
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Braided hoses ordered from bike torque. Very interested in the banjo bolt with the bleed nipple fitted. Will possibly have to get me one of those.
got the braided hoses fitted, bled the system, and....... not much better. The lever doesn't quite come back to the bar, but it's still spongy at the lever; don't mind this so much, as it's a good indicator of how much braking force I'm giving it, but I expected it to be significantly 'harder' at the lever than before, which it isn't.
Think I need to look at Daves' suggestion about the banjo bolt with bleed nipple. Think my problem is with air at the union of the top of the hoses (two separate lines now, not a loop from one caliper to the other) and the master cylinder body. Any other suggestions? please dive in!