STRider
Site Supporter
I suspect you're right on the thread locking compound being the cause. And yes, the rear caliper stopper bolt is listed as "NEW" in the service manual, indicating one time use. A legal CYA for Honda given that these fasteners are related to the braking system.
I see no legitimate, compelling reason why a stopper bolt should be one time use, other than Honda can't ensure that anyone servicing these parts will use the proper type and amount of threadlock that is equal to the OEM from-the-factory spec.I've never replaced that rear stopper pin on any of my ST1100s - 435,000+ miles between the four of them.
I think cylinder / cylinder head bolts and studs are among the few (notice I didn't say only) fasteners that truly justify replacement because to meet and maintain their torque specs they must deform during their installation.