ST1300 rear brake disk hot temperature

My 2003 ST1300 (non ABS) has 102,000 miles on it now and I recently found a very hot rear disk while I was on a weekend ride. I couldn't feel any difference in the usual operation of the brakes but thought I noticed a drop in gas mileage. So I checked the rear disk and found it very hot to the touch. After I got the bike home I started to research the problem through the forum here and decided to call Larry (Igofar) and see if he would help me find out what (if anything) was wrong with my brakes. I can't say enough about Larrys' help and know many of you relied on his expertise also. I have bled (flushed) my brakes and changed pads but that was the extent of my maintenance experience. After talking to Larry I began to work through his trouble shooting procedures and the disk is running cooler now and I feel much better about the health of the braking system.
Before I discovered the hot rear disk I had flushed the system and I'm not certain I got a good bleed. It is possible that I did not get a proper bleed. The first suspect was the SMC. I took it apart and found no corrosion under the boot and the piston moved freely in the bore. Since the bike is over 100,000 miles I followed Larrys recommendation and replaced the SMC. I checked the pivot needle bearings on the left caliper assembly, it all looked good. I added fresh silicon grease to the bearing and checked the top mounting bolt and washers. I bleed the system again, only i pumped the lever and pedal to bleed versus the Mity Vac vacuum method. I then pulled the rear caliper, cleaned and greased the sliding dowels and replaced the pads with new OEM Honda pads. I also ordered new OEM pads for the fronts and changed those, cleaned the pistons and lubed the sliding dowels.
I'm not able to say which if any single thing that was changed solved this hot rear disk issue. I did a lot of test rides and started using an infrared temperature gun to see if the disk temperature decreased and it did. Is it normal now? I can't say what that normal temperature is if you just jump off the seat after a ride and check it?
My disk temperature went from 71F (cold) to 88F after a 10 mile ride (no hard braking). The maximum temperature I read was 117F before most of the maintenance was done. It was just a crude method of trying to get some relative meaurements to verify improvement. I'm sorry to be long winded here but I mostly wanted to share my observations and thank Larry for all his knowledge and help. He really hung in there with me by phone, text and PM during a pretty lengthy process.
I know it's not easy guiding an Olegeezer with limited skills through a braking system this complicated.
Safe riding and efficient braking to yuns.

You are much much more high tech than me!

Had rear brake issues with my 03 years ago while still under warranty, that resulted in multiple trips to the dealer.

Only thing I did to convince myself it was finally fixed, is stop from time to time and spin the wheel by hand and make sure it was as free as when the bike was cold before the ride. If not, it was back to the dealer. Also span the rear wheel on other STs for comparison and get a feel for it.

When I changed my brake pads the first time after only 16K miles , I noticed a staining or build-up of road crud around on the exposed ring around the 3 pistons that would make the retraction of the pistons difficult and maybe not releasing the pads from the rotors. I cleaned that off so they could go back in the cylinders without getting stuck - out . ( Been doing my own brake jobs on my cars and bikes since 1971 , you got to clean them up so things slide as designed , also the pad tab slides )

With all due respect for all your efforts to resolve your brake problem, l have to question why you changed the SMC before doing everything else that tou did to alleviate the problem. If it appeared to be okay and functional when you initially checked it, replacing it would have been a desperation option for me. You may have replaced a perfectly good component. One thing that you didn't mention that I have never been very consciousness about because I didn't know at the time is verifying complete bleeding/flushing of the PCV. I'll try to make a point of keeping that in mind next time I service my brakes.

Don B said:

With all due respect for all your efforts to resolve your brake problem, l have to question why you changed the SMC before doing everything else that tou did to alleviate the problem. If it appeared to be okay and functional when you initially checked it, replacing it would have been a desperation option for me. You may have replaced a perfectly good component. One thing that you didn't mention that I have never been very consciousness about because I didn't know at the time is verifying complete bleeding/flushing of the PCV. I'll try to make a point of keeping that in mind next time I service my brakes.

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I had read quite a few threads about others having trouble with the SMC. Igofar recommended changing it and I agreed because the bike has 100,000 on the clock.
I also changed out a perfectly good fuel pump at 100,000 similarly as a preventive measure and peace of mind. I ride long distance for long periods of time and just like to feel more at ease about components that I feel have a higher probability of failure. I also nicked the rubber boot on the SMC while I was fooling around with it. Who knows it may have went another 100K?

I think? i got a good bleed on on the PCV using the MotionPro bleed valve and the pedal pumper method. Larry gave me the MotionPro tip too and when the Guru speaks, I listen.

olegeezer said:

Larry gave me the MotionPro tip too and when the Guru speaks, I listen.

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Wise words right there! I too am a Larry/Motion Pro disciple! If Larry could walk a complete novice like myself through these complicated brakes he can help anyone!

I've read on the forum that 160F or less is good for the rotor with little to no braking. Mine is generally cooler. It's merely warm to the touch after stopping with only one short distance braking. Wheel spin, controlled stopping, SMC stopping the wheel spin, and temp are my tests for a functioning brake system.

I try to rock my rear caliper regularly, and give it a sharp tap once in a while if it's solid, I think the dowels stick so the caliper doesn't float freely.