Riding a motorcycle bike, I'm sure we can all agree is an exhilarating experience with you being part of the machine and the machine being part of you! This kinetic relationship relies on the machine working as it should in a predictable manner or the consequences can be dire. Unbeknownst to you lurking within your bike are hacks and home brew remedies performed by the previous owners that just don't meet the standards of safety and workmanship.
One of my students was discussing with me a problem he was having with his bike losing power after leaving it in the rain once. This could be cause by a faulty fuel, spark plug, electrical wire system or clutch fault but he was finally able to trace it down to having his rear brake binding. Upon inspection what I found is that the rear brake lever was pivoting to apply the brake but not releasing; it was binding. Now this could be caused by the caliper which is mounted astride the disc and holds the brake pads which squeeze the disc to a halt, but that was not the case here. The brake lever was not moving freely and my approach is to try the easy and cheap remedy first and then proceed to the more complex solutions. So I tried lubing the pivot point with WD-40 Lithium grease and worked the pedal by hand. That didn't help much. I then realized that the problem was more serious than it looked at first glance and more dangerous. The brake which acts to save us, by slowing us down or stopping was set up to be an enemy, which could potentially harm us.
So lets dig into this..
When you apply the brake with your foot or your hand you apply a force that gets transmitted via hydraulic lines to the caliper that is mounted on your disc. The caliper holds one or more pistons that translates your foot or hands force into work by pushing the pads into the discs and friction slows you down. When you release the brake the pressure is removed from the piston and then the pads gently glide on the disc with a minimum amount of drag.
If however the brake binds and the pistons fail to release the brake pads from the disc you not only lose power, you will also wear your brake pads and disc faster but worse the friction will overheat your caliper which will cause the brake fluid to expand and possibly boil as temperature exceed 400 degrees. This can result in a brake lock up or in an extreme loss in power that could lead to an accident. Remember brakes are for intermittent use which means you apply them and then they get a chance to cool off. So they can work as they were intended.
We haven't taken the brake pedal assembly apart yet but what I suspect is that it either has a worn bushing assembly or that the bushing may not have been properly installed. The foot peg acts as a carrier for the brake pedal but is also bolted to the frame or case of the engine. There has to be a set up so that when the pegs is cinched up to the frame that it does not interfere with the free movement of the brake lever. It has to have some clearance so it can move freely. There are various schemes to achieve this but sometimes shit happens and bikes go over and hardware gets damaged. If the bikes is older sometimes the right parts get hard to find and new replacement assemblies get expensive. So some folks apply midnight engineering and will use a washer or whatever to make this sort of work. This is where it gets scary as the bike gets sold and new owners think that everything is stock and normal but it is not. This becomes a ticking time bomb.
Holy sh*t now what do we do?
This isn't rocket science but the critical parts of the bike have to be 100% period or you shouldn't ride it. It is important to do a safety check on your bike and either have it inspected by a tech or learn the basics of how to do this yourself and it isn't hard. In the case outlined above what you have to do is apply the brake with your hand and observe that you see the pedal spring back to its normal position. With your hand you get a better sense of the resistance to application and release. If you find yourself having to pull it back with your hand then you have a problem. If you notice that it is spongy or requires a lot of travel to apply you may have air in the brake lines or mechanical slop if you have rear drum brakes which is a completely different animal. Another test is that if your bike is hard to push around without power, the brakes could be binding. If you put the bike up on a jack you can then spin the front or rear wheel and you should be able to move it with your hand. It won't spin like a bicycle wheel because of drag from the brakes but it move with slight effort. In most cases these are easy fixes and even if it costs you a few bucks look at the alternative of crashing your bike and ending up in the hospital. Big, big costs. If parts are no longer available and a replace set gets pricey you can take the worn or damaged part to a machine shop (or use ours) and make a new bushing. Costs about $25 to do it right, DIY about $12. A machine shop can also engineer a part that is missing for slightly higher cost but they will need the peg and brake lever. So the fixes can be cheap and good to restore the mechanical function to where it should be.
In conclusion, what I want to emphasize is that you should know your bike and have an understanding if there is anything that is the least bit hinky. You don't want to have hacked wiring or a bunch of aftermarket stuff that was duck dynastied on your bike and could fail at anytime. When the motorcycle brakes work as they should they are more linear in their response and therefore safer in getting you out of squirrely situations and that is what matters. Be sure to check yours today and ride safe.