1 Front brake woes, help please Mon Jun 19, 2023 6:14 am
KiwiK100
Gold member
Hey all, I’m helping out a mate who’s having problems with his front brakes. Ok, it’s an 84 boxer, but the brake system is very much the same as a K bike with identical parts used.
The problem is that the front brake pads start to tighten up against both rotors while riding with very little use of the brake lever and takes about 10 minutes to occur. The bike will be forced to a standstill but releasing the banjo at the mc resulting in a squirt of brake fluid fixes the problem for the rest of the ride, only to reappear the next day. Also, if left to cool down the callipers will release their grip on the rotors, it will reappear later. Note that BOTH rotors are hot indicating (in my mind) that the problem lies in the master cylinder. Work so far includes a master cylinder rebuild kit, both callipers have been stripped with new seal kits installed, and the bike runs braided lines albeit the lines were fitted some years ago. The calliper pistons are bores are all good. The only thing left is the master cylinder itself although it seemed fine when I fitted the new piston with no scouring. The return hole to the reservoir is clear. What have I missed? All help and advice much appreciated.
The problem is that the front brake pads start to tighten up against both rotors while riding with very little use of the brake lever and takes about 10 minutes to occur. The bike will be forced to a standstill but releasing the banjo at the mc resulting in a squirt of brake fluid fixes the problem for the rest of the ride, only to reappear the next day. Also, if left to cool down the callipers will release their grip on the rotors, it will reappear later. Note that BOTH rotors are hot indicating (in my mind) that the problem lies in the master cylinder. Work so far includes a master cylinder rebuild kit, both callipers have been stripped with new seal kits installed, and the bike runs braided lines albeit the lines were fitted some years ago. The calliper pistons are bores are all good. The only thing left is the master cylinder itself although it seemed fine when I fitted the new piston with no scouring. The return hole to the reservoir is clear. What have I missed? All help and advice much appreciated.
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Current rides:
2020 R1250RS. Metallic black with all the fruit
1983 K100C. Red. Krauzer fairing.
1984 K100RS. Madison silver.
2002 K1200RS. Owned from new. Pacific Blue, Ohlins, Speiglers, Fiamms, HID. 186,000km SOLD
1991 K1. Schwartz metallic black, 18 month frame off restoration. 74,000km SOLD
1987 K100RS Style. Black, Ohlins, Race Tech springs, Braided lines. Fully restored. 53,000 miles. SOLD
The family history:
1951 AJS 500 single - my Dads ride
1953 Triumph Terrier - my Mum's ride
1916 Triumph Type H, Battle of the Somme, France WW1 - my Grandads ride