Brake caliper chatter during braking and/or low speed turns

On my 1982 KZ440 G1 I recently had the front end removed for steering stem bearing replacement. The front disk brake worked totally fine before removing the caliper from the forks. The caliper sat for a few days with a wood shim between the pads to keep everything in place.

After putting the caliper back on the front disc and torquing everything to spec, the brakes will now chatter on intermediate to hard braking at any speed. The brakes also chatter at low speed when turning left or when turning the bars from left back to center. The chatter sends vibrations up to the handlebars and is quite audible. There doesn't seem to be any great decrease in stopping power--there is only this terrifying chatter.

What's going on here? KZ440's have a single front disk with single piston. I plan to disassemble the caliper in the next few days to regrease the slides, and put it back together.

Have you check for bad wheel bearings?

I checked wheel bearings by muscling the front wheel around to check for play while the front end was off the ground and everything feels good.

Today I went for a ride after greasing the slides and cleaning the disc and pads, but the problem persisted. When I was in a parking lot doing slow speed maneuvers and braking to figure out what was going on, I found I could push the bike with it shut off and get the weird rattle when I turn, but not only that, I just noticed the front brakes are DRAGGING! Very lightly so you wouldn't notice with the engine on or feel the bite while riding.

This caliper has been apart once before, a few years ago, and got a new cylinder, fluid seal, and dust seal. Looks like I'll have to go down that road again to fix the stuck brakes, and hopefully that'll resolve the rattling/chattering problems too.

What did you clean the rotor with?
Was there any fluid on the wood shim?

In response to F64, I cleaned the rotor and pads with CRC 05089 BRAKLEEN Brake Parts Cleaner - Non-Flammable and then I let them air dry. There was no fluid on the wood shim.

Additionally, I have some updates and I am in need of brake wisdom. Per my last post, I rebuilt the brake caliper: new piston, new fluid seal, new dust seal, new caliper slide boots, new grease. The old piston I removed had some pitting on it. The cylinder in which the piston slides is clean.

But the problem persists! Brakes/pads seem to chatter or rattle at all speeds while breaking. The weird part is they chatter with the bike off WALKING the bike around the pavement and turning the handlebars. The brakes still have a very light drag. They do not become MORE draggy though--they always just barely drag and is audible only with the bike turned off. Upon inspection of the pads I noticed a very slight blue shading on one part of the brake pads, likely where it is dragging and heating up.

Wise brake mechanics, please help me! This bike is nearly perfect in every other way and I can't wrap my head around this problem or how to fix it.

Probably a dumb question but are there any small parts missing from the assembly?
I'm thinking specifically of 92081 which Kawasaki call a spring pad and which the Haynes manual calls an Anti Rattle Shim. Also the other item in red circle. Kawasaki - guide. Haynes - shim. These can easily go missing during brake service but I'm not sure what effect their absence would have.

Chatter is usually a symptom of rotor warp. If your brakes are indeed dragging and rotor got hot enough to blue then it likely warped. do you have a dial indicator? measure the runout of the rotor.

A bad front MC? Plugged ports?

Verbiage in describing problems sometimes becomes an issue especially in dealing with brake problems. Chatter can mean several things. What are you actually "feeling" when you experience this problem or is it just noise? Many times chatter can be a warped rotor or a rotor that has a surface imperfection on one or two sides. When you apply the brake at speed you will feel a hurkey-jerky sensation or if it is bad enough the brake lever or pedal will go all the way down to almost nothing with little to no braking action. Rotors can bend or warp quite easily if you aren't careful even by contacting a wheel vise on a lift. Almost all disc brake systems have a little bit of brake drag as you call it because the pads don't fully retract on both sides of the caliper. To compound the situation dust and dirt can get in between the pad(s) and rotor and cause squeaking that will drive you nuts. Sometimes in these situations a quick cure is to get the vehicle up to speed and apply the brakes quite hard. Be careful doing this as you don't want to experience a wheel lockup doing this. Do this several times and see what happens. This also helps if the pads are glazed over at all and will remove the glaze that can cause issues also. Depending on the quality of the pads the glaze can return in varying time periods. Personally I wouldn't worry about a little bit of brake drag, but if you have to forcefully overcome brake drag when you rotate the wheel that could indicate a problem. A little bit of resistance isn't the end of the world. Make sure all the components are present in your system including the anti-rattle clips, but even if those are missing it shouldn't result in faulty braking action, just unwanted noise. So what are you actually feeling in the brake when you are braking? Is this just a noise issue?
Rick H.

No missing parts from the caliper assembly--I have the anti-rattle shim/spring and everything is complete. Master cylinder is aftermarket from eBay, two months old.

The chatter when braking at high speeds is both a feeling through the handlebars and a loud high or low frequency vibrating noise. At low speeds when walking the bike in a parking lot the noise is more of a clinking/spinning sound. While turning at low speeds it almost sounds like one pad is bouncing against the rotor.

Looks like the next thing I should do is measure the runout of the disc. I don't have a dial indicator but I'll do a rough inspection with a pen taped to the fork. Does anyone know about getting an aftermarket disc for the KZ440 if getting a good quality used rotor isn't an option? Is it also possible to remachine the rotor to make it better?

You could remove the brake caliper, tie it up to relieve stress on the hose and walk the bike up and down the drive way. Watch the disc for signs of warp or runout. If the noise disappears then is possible it something in the caliper. Put the bike on the main stand and get the front tire off the ground and check the front rim and rotor while spinning it. What I’m saying is take parts one at a time out of the system till you find the trouble. When you had the triple tree off, getting the upper fork tubes at the same position in the upper tree is critical and then you tighten the lower clamping bolts. See photo. I know it’s not you bike but I’m sure Install procedure has to be similar.

astrosail wrote: No missing parts from the caliper assembly--I have the anti-rattle shim/spring and everything is complete. Master cylinder is aftermarket from eBay, two months old.

The chatter when braking at high speeds is both a feeling through the handlebars and a loud high or low frequency vibrating noise. At low speeds when walking the bike in a parking lot the noise is more of a clinking/spinning sound. While turning at low speeds it almost sounds like one pad is bouncing against the rotor.

Looks like the next thing I should do is measure the runout of the disc. I don't have a dial indicator but I'll do a rough inspection with a pen taped to the fork. Does anyone know about getting an aftermarket disc for the KZ440 if getting a good quality used rotor isn't an option? Is it also possible to remachine the rotor to make it better?

Measuring disc runout on the bike is an exercise in futility. You would need to absolutely lock the front end tight so there is no side to side movement with the front wheel off the ground. If you know of someone that has a truing stand see if they will put your wheel and rotor in it and connect a dial indictor to stand and measure rotor runout that way. You can also dismount the rotor and put it on a flat surface and try to sneak feeler gauges under it, or use a straight edge on top of it with feeler gauges. Very difficult process either way. A truing stand is best option. A motorcycle shop should be able to do this quite easily.

I must ask though, are the pads of high quality such as OEM? Are you absolutely certain the wheel bearings are up to snuff and all spacers are correct and in proper locations? Are the fork tubes installed correctly? Don't forget to check your axel for straightness. A slightly bent axle will give you fits at times.
Rick H.