82 650 Maxim Front Brake Issue

My front brake takes a lot of force on the lever to slow down, you really have to squeeze with all 4 fingers to stop. My 82 750 Kaw will dive the front end hard with little force from one finger. I've rebuilt the MC and Caliper, replaced the lines with SS ones, bled the brakes successfully (it is not spongey) and put on new pads. The rotor is within spec but there are grooves in it and the surface is wavy. I'm wondering if the wavy surface is limiting the contact area of the pads and reducing the braking force. Does that sound reasonable?

 

I do believe that you are correct. Not all auto parts stores have machine shops anymore, but most towns do have a real machine shop tucked away somewhere. If the rotors are still within service limits, have them trued up.

 

Thanks. There's a couple small pop/son shops I worked with during the build, I'll reach out to them next week. Hopefully that solves it.

 

I completely rebuilt the brakes on my XJ700N -- calipers, m/c, stainless lines, pads-- and they work well but do take more force than my Hondas. My rotors are smooth. Maybe I'm mistaken, but I think these brakes just take a little more force than some the the newer ones. Still, it wouldn't hurt to have your rotors reconditioned.

 

I've got a 82 650 with 750 forks with stock rotors calipers and master mine don't take much force my calipers are about shot tho I pulled them apart sanded out the rusty spots regreased them stuck em back on ..they still need to be completely rebuilt but that's another day.. as far as my master cylinder goes it hasn't been rebuilt either and is missing the rubber seal for the lid I used build your own gasket had to double up and turn my lid backwards to get it to seal up mounted on pretty much flat bars

Since im talking about my brakes im not sure what causes what im about to say here hopefully someone will know tho my brakes don't always release like they keep building more and more pressure all I have to do is crack one of the bleeder valves and it's back to golden so I might have to do this two or three times and they are usually fine after that

 

Sounds to me like your m/c needs to be rebuilt at a very minimum. When you release the brake the m/c should allow the fluid to return to the m/c thereby releasing the pressure on the brakes. If you still have the original brake lines they could also be coming apart inside and preventing the release. I sure would not be riding it like that. If you can only do one thing, then I would rebuild the m/c first since it seems that the calipers are moving freely when you crack the bleeder valve. It's a fairly easy job. Chacal has everything you need.

 

less surface area contact you hit it on the head.
of course when your pads wear into the grooves and waves braking will improve.

what kind of pad did you use?

 

I would be okay if it required a little more force than my other bikes but we're talking super manly grip to slow this thing down quickly. I would not trust my wife to ride it at this point.

HCP1706 Aftermarket standard organic front DISC BRAKE PADS SET

 

good pads.
i may have a manly grip but i can brake with 2 fingers. should be able to stop bike with in mfg specs easy.( With out down shifting)
you do have to use the rear brake as well, I see it overlooked by many because it is "Only 20%" of your braking power then there is the down shifting as well to slow you.
the most important thing you can do is keep a good distance.

 

I ended up replacing the rotor after a few dead ends on getting the original and while it's slightly better, it's still not what I would expect. The rear brake is more effective and my hand hurts between my thumb and first finger from squeezing so hard from the last ride. Any other thoughts? The MC is from a turbo bike, has a 5/8" piston so it's a little larger than the stock 14mm but I would think that would give it a lighter feel. Everything is rebuilt, new lines, rotor is an EBC MD2023LS.

 

A lager MC piston will make the lever harder to squeeze.

 

^ yep.

 

Yes.

You really should replace pads when you replace the rotor, and in any case, you need to "break in" the pads according to EBC's instructions.

 

Pads were new when the caliper was rebuilt. About 300 miles on them before I swapped rotors ( I know mileage is a tough indicator of use but I have no idea how much brake time happened since then). Do you know what the "break in" procedure is?

Balls. I guess that makes sense, more fluid movement with less piston movement. What "flat" style MC should I look for then? Anyone need a powdercoated fully rebuilt MC?

 

http://www.thumpertalk.com/wiki/_/breaking-in-your-brakes-r107

 

Balls. I guess that makes sense, more fluid movement with less piston movement. What "flat" style MC should I look for then? Anyone need a powdercoated fully rebuilt MC?[/QUOTE]

I could use a MC

 

I'll post it up for sale when I do swap. Still figuring out what way to go so it will probably be awhile before I do.

 

I'm convinced the MC is too large, I read in multiple brake sizing documents that the larger piston moves more volume and a smaller piston creates more pressure. I would be fine if I had a larger caliper or dual discs but I do not. I am outside the "zone" for adequate braking. Unlike a typical vehicle MC, I cannot change the mechanical advantage on the piston either.

I'm trying to stick with a Yamaha OEM master cylinder from the same era to keep that stock look. From what I can tell I cannot find a similar bike that had a 14mm MC with flat bars. The 550 Seca has a 13mm piston which should bolt in place but has a 8.85% decrease in diameter. I don't know enough about brakes to know if this will make the brakes touchy or downright dangerous (i.e. wheel locks too easily). I can say going to the 5/8" piston which is roughly 13% larger has made it difficult to stop.

Any thoughts?

 

I am not convinced that using a 16mm m/c will make that much difference in the brake lever effort as you describe, I think there may be some other factor (caliper piston seizure and/or glazed pads) in play. The 650 Max has a caliper piston that is about 33% larger in area than 550's or 650 Turbo models (although in the 650 Turbo instance, there are 2 calipers, each of them is about 33% smaller than the 650M caliper piston).

 

I'd be glad to look at anything else, I'm not too excited about replacing the MC. The caliper should be okay as it was rebuilt with a new piston that slid in fairly easily. Brake jobs in the past have gone well so I don't have any experience with glazed pads/rotor. Is it as simple as pulling them to see if they are glazed over and removing if they are?

 

Pretty much, yes. But de-glazing them can be tricky, depending on how glazed they may have become. Typically you have to rough-up the surface with a coarse grit material to remove the glaze....while keeping the pad surfaces flat and true.....and then perform the breaking in or "bedding" process again:

http://ebcbrakes.com/articles/motorcycle-bed-in/


Organic pads also can suffer from "green fade" phenomenon:

Green Fade occurs when organic pads, that have not been properly bedded-in, reach temps that are high enough to cause the pad binding chemicals to “boil off”. This off-gassing creates a liquid state between the pad and rotor, which will logically (and rather suddenly) result in greatly reduced braking power, and may even cause a slick glazing of the pad. Gradually bringing the brakes up to maximum operating temp in the last 5-10 brake applications of the bedding-in process allows the gasses to be burned off without glazing the pads or complete fade.

Glazing refers to when the pad surface becomes extremely hard and “slick” (frictionless) from rapid heat build up. Since great braking is all about great friction. you can easily appreciate how a hardened, slick pad material will cause serious braking problems. In some (but not all) cases, glazed pads can be salvaged by removing them, and then block sanding them with coarse sandpaper (150-grit), but……… replacing glazed pads is the recommended solution. Please note that modern fully-sintered pads do not utilize chemical binders and thus this type of situation does not occur with pads made from those materials…….it only applies in the use of organic pads.

To perform this part of the procedure, accelerate your bike up to about 50-60 mph and then bring the bike down to about 5 mph by applying the brakes at about 60-80% stopping power. Cruise back to your starting point to allow some cool down time between braking runs. Do this about 5-10 times and gradually work your way up to applying maximum braking force without locking up the tires or coming to a complete stop. IT IS VITALLY IMPOTANT THAT YOU DO NOT COME TO A COMPLETE STOP DURING THIS PROCESS!! Find an empty parking lot or similar to do this at........


So to re-cap:

- "bedding in" new brake pads allows the "hills and valleys" within the pads or the rotors o be reduced via erosion and "fill in", and will thus tend to equalize (and MAXIMIZE) the contact area between pad and rotor, thus ensuring maximum friction.

- bedding in of ORGANIC pads requires creating rather extreme brake pad temps at the end of the above "bedding in" process to burn off chemical binders used in the pad material.


The basic process of bedding in pads and rotors is to accelerate your bike up to 40-50 mph and then bring the bike down to about 5 mph by applying the brakes at about 60-80% stopping power. Cruise back to your starting point to allow some cool down time between braking runs. Do this about 10-15 times and gradually work your way up to applying maximum braking force without locking up the tires or coming to a complete stop.

It is extremely important that you do NOT bring the bike to a complete stop using the brakes during the bedding-in process. If the bike comes to a complete stop with extremely hot brakes, it’s possible to transfer a large amount of pad material to the rotor in a very small spot, resulting in an uneven thickness of the rotor. This can lead to pulsatiing and inconsistent brake performance. Left unchecked, hot spots can develop that will permanently damage the rotor. If you catch it early, you may be able to remove the excess pad material by dressing the rotor with medium grit sandpaper (800-1000 grit) followed by a thorough application of Brak-Kleen or similar.

 

Thanks Chacal, I'll pull it apart tonight and see how the pads look.

 

I'm no expert but I would guess these are glazed over. Cleaned them up with sandpaper on a flat surface and cleaned the rotor with brake cleaner. Hope to try it tonight but lost the dang retainer spring.

 

Not much change after sanding the pads and cleaning the rotor. I followed the instructions on EBC site (very similar to above and other forums I read) and I do see some transfer of material to the rotor but really no improvement in braking. When you first pull the brake lever, you can hear the pads hitting the rotor but there is no grab. Only when you muscle it in do you get some reduction of speed. You really have to squeeze to get the bike to slow down, way harder than my other two bikes. Unless I really force it, the rear slows me down much easier. Any other thoughts before I go the MC route?

 

I think it's the MC. A small difference in diameter equates to a big difference in leverage.

 

Post deleted due to a brain fart.

Gary H.