1977 R75/7 I noticed a couple of weeks ago I either had no brake light, or a brake light that would come on a couple of seconds after I squeeze the front brake lever. Sometime I had to squeeze it extra hard to activate the light. The rear brake and light work fine. Today while servicing the throttle cables and tube, I checked the front brake for illumination and got nothing. Test light shows current to the switch, but none out when lever is squeezed. I jumped or bypassed the switch and got brake light. Front brake works fine as far as stopping goes, so master cylinder is good. Just no brake light from the front brake. I'm inclined to think it is the switch, since it appeared to slowly go bad. But before I order a new one, I'm just wondering if there could be another problem besides the brake switch? EDIT: It turns out to be the brake light sending switch on the master cylinder under the tank.
I just fixed both the front and rear brake switch, neither of which would make the lamp light up, and both the front blinkers. The rear switch just needed a squirt of cleaner. The rear lamp and blinker lamps needed cleaning and re-seating. the front switch's wires were shot as the entered the switch. I needed to remove the whole wire and re-solder them to the switch, new shrinkwrap and then clean and grease the whole area where the brake lever hits the switch. I metered continuity and 12v throughout the process, and made sure the switch was functional, etc... I needed to clean the connector where the brake light switch hit the harness, and then also the next connector up the line from there <-- Hows taht for a kick in the ass 2 and a half hours or something, and i didnt even got to fixing the horn.
I've never been a fan of switches that are actuated by fluid pressure. There's always a lag between the time you pull the lever and when the lights come on. That being said, old switches of all types do wear out over time. Odds are that the new one will do the trick.
I replaced my pressure switch on the R65 for the same reason (rebuilt the rear switch). It is hard to get the air out of the system until you lay the bike on the throttle side because it is stays in the pressure switch. Burped once and good to go with brake lights functioning from front and rear activation.
Wonder if there might be air in the line/switch? Might explain why I had to pull the lever 2 or 3 times before it would work. I had a Corvette once that never leaked brake fluid, but kept getting air in the lines. Turned out the calipers and pistons were etched and only a new set of SS calipers were the fix. I haven't messed with the front brake caliper yet--- just replaced the pads even tho they were good, just old. Thanks for the replies. EDIT: I just went out and pumped the lever a whole bunch, and got brake light. I think I will do another bleeding of the line and see if that solves the problem. Brake fluid change and bleeding was done last fall, and I put about 500 miles on the bike since then. Just noticed the problem after the bike sat all winter.
Wait a minute. The pads were good, but old. So you replaced them. if they were good why did you replace them? If they were old, why did you consider them good? (they don't age BTW)
Just stupid, I guess. But then they looked like they had 28,000 miles of use on them, so since I was doing a bunch of other stuff..........
Pads absolutely DO age. They absorb moisture and end up dragging a lot. The backing plate starts to rust from the inside. Every year I replace a few sets of new-looking pads for this reason and there's a night and day difference.
Thing is, the old pads were bedded in to the worn disk. The new ones are going to have to get bedded in to the worn disk. So initially poorer braking while that happens, large initial pad wear and minor accelerated disc wear (might not hurt to knock the ridges down a hear tho'). Also you moved the piston travel back to the top of it's bore where it's already been, you you are not evening out the wear over the length of the bore. This is likely a more minor issue however that bore has a texture that helps with lubricating it. The more worn top of the bore is slick so poorer lubrication up there. The less worn lower bore still has texture. When you rebuild the caliper, you very lightly re-texture the whole thing. Again, likely a minor issue. If you saved the old pads and they are clean. I'd put them back. Save the new ones, their day will come. Nothing lost or wasted, you got to clean things up (like the pins, get those to zero corrosion then grease them) and now with the experience changing them is a snap. if the switch is getting old it's element won't move a nicely as a new one. If you get a little air bubble in there, it may compress enough to give erratic function. You can tru tappiy int lightly or bleeding it by unscrewing it a bit and applying brake. Brake fluid eats paint and attracts water and thus rust. I prefer mechanical switches. last a long time, easy to replace. Trick is how to rig them. You can set up a microswitch (check out the Cherry line) to sense brake lever travel. And they are very small. You can also use a magnetic reed switch and those thing are incredibly small. Think unubtrusive. Just glue one on. I generally set my switches so they trigger the light well before the brake is actually applied. This lets me flash the brake lights when I'm not actually braking---like under hard engine deceleration or sitting at a stoplight with someone coming up too fast in the mirrors. I flash the brake light, clutch it and begin to roll on the throttle all at the same time.
Have you ever seen this condition on an auto? (daily driver) When you see draggy fronts on a bike, look at the rear. Whole lot of wear there? Those pads get very hot...if they get used. If they don't get used, or if the bike has been sitting long in the damp, all bets off. Try taking some of those damp pads and doing some seriously hot braking with them and see what happens. Like trail them at medium pressure under throttle. I had a very serious problem at one time with grabby brakes at low speed when damp on my /5. I made inquiries of brake/clutch people to see what might be done. (sales reps, engineering degrees, industrial brake and clutch systems). My official problem had to do with slip clutches on machines that got soaked every 8 hours with a disinfectant wash. I slipped the bike question in on the side. Answer was: nothing to be done. You have to use them and dry out the material (or bake them in an oven). So I got rid of the front drum on the /5 and fitted a disk.
Caliper not returning fluid to the MC? ASAIK, disc brakes are supposed to drag ever so slightly. That's why they squeak sometimes and there are a zillion products to put behind the pads to shut them up. The pad is not dragging precisely evenly on the disk. So it chatters at high frequency and makes a squeak/squeal noise. Can also happen when applied or only when applied.
Yes...in answer to your question. Do you have a Clymer?? There is a way to modify the brake lever. Look at the bottom of page 423 Brake lever modification. I had to do it years ago and have never had a problem since. It involves filing down. If not, I can scan it for you.
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To answer my own question: I finally got around to replacing the brake light switch on the master cylinder to the front brake. It fixed the problem. Thanks for the help from all.
