On my way into Worcester today, bike seemed a bit strange, saw smoke in the mirrors. Pulled over, caliper was basically on fire. Once I got the bike home and pulled it apart this is what is left of the pads - two bent up pieces of metal. The pistons are toast also. I can’t find any rebuild kits on eBay but after the heat it experienced I’m thinking just to get another caliper. There’s a couple on eBay, but does anyone have a spare they can sell me?
The question I'd ask is: what caused this. I'd hazard a guess that the rear master cylinder is faulty and got stuck.
I think I’m to blame. I fitted new rear sets and I think the brake lever pivot that holds the brake light switch, was binding which let the pads stay in contact with the disc.
I did exactly the same a couple of years ago on my 749R. Caliper, pistons, pads and disc complete toast. Had just fitted rearsets and hadn't adjusted the plunger on the brake.. Replaced the lot with second hand.
not enough free play in the master cylinder pushrod is a common one on 748/916 etc, and more likely to happen on a hot day. There are several threads on here about this.
that will almost certainly be it, sorry to say. I used to find that factory spec adjustment was still not enough if ambient temperature sky-high.
I had this on my 748, bike felt slow, I stopped and looked down and the disc was white hot, didn’t have enough free play in the Master cylinder was tbe fault
Had this on a track day, I got flagged down by a marshal and my caliper was on fire! Luckily rear disc was Ok but the rest was finished. Best to replace the rear caliper and pads and anything else, the rear brake isn't much good at the best of times but it's better than nothing at all.
Quite common, I'm afraid. On my way home from the first service, the same happened to my 916. Gradually slowed down until, at a roundabout it wouldn't pull away as the rear wheel was locked. Looked at the rear brake and the pads were on fire. They had adjusted the rear brake to remove some play, I hadn't even used the rear brake in the 5 or so miles I had travelled when it happened so it was purely due to dragging causing heat build-up etc.
I've got a new caliper, everything connected, but I just cannot for the life of me bleed this sucker. I currently have the caliper off the hanger, upside down, zip-tied to one of the exhausts, but no fluid is getting to it, nor is the fluid level going down in the reservoir. If I pump the brake, I can hear air coming out of the bleed nipple. If I take the nipple off and use a gloved finger to block/unblock the hole I can feel vacuum/pressure. Is it a case of needing to do something special if all the fluid has been out of the master cylinder? Does it need priming? I've even connected a vacuum pump to the bleed nipple to try and pull fluid through, but its just getting air.
If the system's completely empty, I'd pop the caliper lower than the master to let gravity help the fluid get to the caliper. Then bleed it as you have been trying to do oncve it's full.
Get a syringe, connect it to the bleed nipple and fill it from there, effectively pushing the air through to the reservoir. Then just purge the system by the normal procedure.
I had exactly the same happen to me on the Raptor & replaced the caliper for a brand new one. If my memory serves it wasn't that expensive either for the peace of mind it gave - 60 sovs or so. But in my experience it is best to have the caliper above the master cylinder when bleeding it out with the bleed nipple at the highest point. It is a bit of a faff setting it all up mind, I tied the caliper to a small set of steps. And a Kikkoman soy sauce bottle is great for the fluid as they're really stable & hard to knock over.
