Anti-Dive Noise

My '83 XJ750RK Seca forks seem to be performing the way they're designed, yet thay make an annoying clicking noise when the anti-dive mechanism is activated. With only 11K miles on the bike, every inspection reveals what I'd expect--absence of corrosion or wear and free moving parts. I've even removed the plunger assemblies from the top of the dampener assemblies to check for free-moving internal parts--no apparent problems there--as easily as I can work the plunger with my fingers, I'd expect a more progressive action as brake fluid pressure changes. But it acts more like an on-off switch accompanied by that clicking. I've tried every setting of the adjusting bolt, which only changes the degree of effect and not the sound of activation. I can learn to ignore it if I find out it's normal.

So 750 Seca guys, tell me if you front suspension talks to you when you're grabbin' a handfull of those double discs. Yes I do use my front brakes very aggressively.

Thanks

 

Are you sure it is the anit-dive? Could it be the brake calipers? If the pad shims are missing it will make a clicking sound when the brake is applied.

 

I'm only sure that it occurs exclusively during extreme fork compression, is only evident when this is the result of aggressive braking, and that the timing of this clicking noise is affected by how I've adjusted the anti-dive.

I've heard a lot of brake noises, but nothing like this.

Although I haven't disturbed the calipers, if the Yamaha-published service manual is correct, I'm seein' the shims properly assembled. AAMOF, the condition of the rotors and the amount of pad lining indicates a likelihood that all this hardware was factory assembled and the 11K odometer reading is true.

I would still like to know if other 750 Seca riders either have or have not heard anything like this.

 

I have had similar noise from anti-dive equipped bikes. Another possibility is the fork springs. The spacers also function as centering washers for the springs. If the springs are not centered in the tubes they can rub the tubes and make noises durring hard braking.

 

That's helpful to know.

I took the springs out and cleaned them when I changed fork oil earlier this year upon buying the bike. I didn't notice any shiny spots--just an even film of 30-year-old, coagulated oil. The forks operate quitely when reacting to big bumps at sustained speed without braking. For it's weight, it's a smooth ride and performs well enough.

 

i don't remember anything in there that could make noise, the only thing loose in the forks is the piston with the wave washers but those couldn't make much noise.
do you hear it or feel it or both?
could it be the steering neck bearings?

 

I'll agree on neck bearings mine used to click going over roll over curbing or sharpish edged holes/bumps and low speed quick stops..now ..tapered rollers and no clicking. It might just need th bearings tensioned a bit tighter.

 

Audible only, can't feel it.

I couln't feel any play or binding when I inspected it during the process of removing the fork tubes from the triple trees, so I didn't see the need to disassemble any farther. If you saw how clean this bike is, you'd probably think that internal corrosion or excess wear is very unlilkely. Other disassebled parts of the bike indicate it's lead a sheltered life.

All speeds & all road conditions, occurring only during aggressive braking/substantial fork compression, and changing in frequency to correspond with different anti-dive adjustment settings--hardly seems like the same problem.

 

How about we go down the, 2 AD. Units but only 1
Noise, road. So if it is normal only 1 does it.
Your not supposed to but maybe turn one up and one down to try to isolate it

 

my guess would be the steerer bearings, upgrading to tapered rollers is something thats nice to do anyway.

 

Mine did it. Turns out it was the caliper shims moving ever so slightly when the brakes were applied. My "no cost" fix was to slide a toothpick into the shim to stop the movement. The clicking disappeared immediately.

 

My guess would be that you haven't read this thread.

I "guess" I'm not that interested in replacing good components that have alreaded passed inspection.

 

Found the noise yet?

 

I've tentatively concluded that either the L or R actuating piston (plunger) is sticking--sounds like the right one. Instead of progressively sliding up and down with changes in brake fluid pressure, it "snaps" to full stroke only after a threshold pressure is reached. Because of the parts availability and cost questions, I had hoped to hear from others who had serviced these before I started any disassembly.

I haven't ruled out the possibility of a sticking dampener piston, but I accessed the tops of these when removing the plunger assemblies. The pistons moved freely enough, but may react differently when charged with hydraulic pressure during fork compression. Yamaha says each can only be replaced as a unit.

This winter I'll take apart the actuator plunger assemblies to see if I can free them up without getting into the parts-availability/cost issue. If not, I've already engineered a clean, solid way to disable these. Even without the anti-dive feature, the Seca has nice, deep, adjustable front suspension.

 

I have serviced the anti dives but not had your problem, they're mechanically simple things. What may cause them being on/off is the O ring on the valve being distorted or such. Others have blocked them off or made their own adjustable versions, you'll have to search for them .. maybe polock and darkfibre.

 

Where did you buy parts for these?

 

If you haven't found it yet, here's a diagram of the anti-dive unit disassembled.
http://www.xjbikes.com/Forums/viewtopic ... rt=15.html

Some of the internal parts aren't available, so you have to be very careful removing them. I've cleaned and rebuilt mine with whatever parts chacal had available, but I don't remember exactly what wasn't available. Chacal will have that answer.

If you haven't adjusted/inspected/regreased/rebuilt/replaced your steering head bearings, consider it. Steering head bearings can fail for many reasons, including corrosion, break down or contamination of the 30 y/o grease, and detents from abuse. The only way to "see" it is to disassemble and inspect. I understand that they pass the "standard" inspection, but if they are wearing on you, given their age, they will wear rapidly and the loss of control for bad steering head bearings is catastrophic. At least have a look at them. And a clunking under high braking load IS a symptom of a steering head bearing failure, so it's best to eliminate that possibility completely.

 

Great photos. They nicely supplement Yamaha's marginal drawings.

"Clunking?" OK I wasted my time describing the issue. I should have entitled the thread "neck bearings and calipers".

Troubleshooting 101: "Check the easiest and most obvious things first." I'm going to confirm or exclude a more-likely, more-easily-remedied cause before assuming it needs a more-expensive, more-time-consuming job. I'm perfectly happy to wait until neck bearing service is due, or conclusively indicated. Anybody who'd actually seen, ridden, and inspected my bike (or even read my posts) might agree.

 

"Check the easiest and most obvious things first." you forgot cheapest
i would think you would feel a neck bearing, not so much hear it.
how about silly things like fender loose, brake lines and speedo cable slapping on something, calipers rattling.
could you tie the front end down with a strap, maybe something will become obvious?

 

I wanted to say it, but only a "Wizard" can get away with that!

It would indeed be silly to start a thread without inspecting these first.

Yeah, but then I'd have to listen to the strap slapping in the wind. :roll:

I think it already has, but just not to everyone.

 

Search on YouTube there is a video on dismantling/servicing the anti dive.

 

did you ever oil the speedometer cable