Rear brake woes gl1100

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derrick woods

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Aug 29, 2022
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Location
Tennessee
My Bike Models
Gl1000
I've been a motorcycle mechanic for a long long time and I have to say I absolutely despise the 81 gl1100 brakes they have to be the single worse brakes I've ever dealt with. With that being said I need some help with rear brake it drags drags drags. No matter how many parts replaced I done new kl master cylinder rebuild cleaned all orifices bore polished return port clean main port cleaned. Brannew stainless braided brake line new caliper rebuild with new piston kl brand caliper cleaned bore polished I don't know where else to go or do
 
The most common reason the '80-'81 rear brakes drag is due to the return port not being open. Not always a matter of cleaning (looks like you did that), it is often the pedal is not adjusted correctly often due to the bushing in the pedal being sticky. If the pedal is even dropped a touch, the return port will not let the brake fluid back to the MC causing them to drag. Simple test, press the pedal with your hand and check resistance. There should be none other than from the return spring. The pedal should move very easily.
 
The most common reason the '80-'81 rear brakes drag is due to the return port not being open. Not always a matter of cleaning (looks like you did that), it is often the pedal is not adjusted correctly often due to the bushing in the pedal being sticky. If the pedal is even dropped a touch, the return port will not let the brake fluid back to the MC causing them to drag. Simple test, press the pedal with your hand and check resistance. There should be none other than from the return spring. The pedal should move very easily.
I think I might have got it sorted out it still had just a tiny bit of air in caliper I flipped it upside down and it must have shook it loose anyway after is sits over night I will know for sure
 
Well I thought I got it soon as it heat soaks it started getting tight again I really don't know what else to do at this point other than buying another caliper to rebuild
 
Push comes to shove, you could always upgrade your caliper and master cylinder. Might take some custom machining, but you could upgrade to some really snazzy brakes. . .
 
And may have to honestly I'm at near loss on it because every internal has been replaced at this point I'm just wondering if it's not a clearance problem with the master cylinder piston just barely covering the return port cause the wheel rolls it just has the slightest amount of drag
 
And may have to honestly I'm at near loss on it because every internal has been replaced at this point I'm just wondering if it's not a clearance problem with the master cylinder piston just barely covering the return port cause the wheel rolls it just has the slightest amount of drag
I know you said that the return port was clear but this sure sounds like a blocked return port problem. I had the same issue on the front brake of my '83. It took a lot of poking in the return port with a small sewing needle (clamped in some needle nose vise grips) to get it cleaned out and then some more work with a piece of fine wire to finish the job. When I rebuilt the rear master cyl it was even worse. I'm suprised my rear braked worked at all. Good luck.
 
As said earlier it's not the return port it's as clear as it gets not to mention I use an ultrasonic cleaner to remove all sediment too it never completely locked up it just had a slight drag when turning the wheel by hand . A slight resistance it turned out to be the factory piston was 4 thousands too long using the new seals. I found an shorter piston installed it and now it is finally operating correctly. Only reason I looked into the piston length was somebody in another post mentioned filing his piston a bit and it worked
 

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