I've ordered the master cylinder rebuild kit for my 1978 R80/7. Is the piston really one piece so that I have to stretch the back cup over the diameter of the piston?
yes,it is one piece. what some folks do is use one of those taper caps you get with a bottle of gear oil or that comes with a caulking tube to act as a guide so the seal slides over the lip easier.
Another trick is to put the seal in a cup of hot water for a few minutes to make it more pliable.
former Airmarshal, IL.
Another trick is to convert your entire hydraulic brake over to DOT 5 Silicone brake fluid so that you never have to worry about hydraulic brakes again. Never have to replace the fluid annually. Never have to worry about DOT 4 fluid eating the paint off your tank and frame. Never have fluid leaking all over and damaging your electrical connections. Etc, etc.
:whistle:
Owning an old Airhead is easy.
Keeping an old Airhead running great is the true test.
Stick with manufacturers recommendation, even though airheads don't have anti lock brakes, DOT 5 can give a spongy feeling brake.
CAUTION: Do not use silicone DOT 5 fluid in an antilock brake system. Operating efficiency will be reduced.
Silicone DOT 5 fluid has some other characteristics that you should beware of. Silicone fluid compresses slightly under pressure, which can cause a slightly spongy brake pedal feel. Silicone fluid also attracts air more than polyglycol fluid does, which makes brake bleeding harder. It also tends to vaporize slightly just below its boiling point; and it will aerate from prolonged vibration. All of these factors mean that DOT 5 silicone fluid should never be used in an antilock brake system
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