Metallic Noise from Fork?

This is so wierd. My '79 750 twin makes a funny metallic noise that sounds like it's from the forks. When I turn it off and if I turn the forks and get off, I sometimes hear a kind of metallic noise that sounds like if you took a screwdriver shaft and tapped the fork tube. It is definitely coming from the front end down low.

I have no idea what it is. It seems to ride fine. I wiggled the front wheel and the wheel bearings are tight. I have adjusted the stem bearings, seemed OK. The fork oil is good. If I hold the front brake and bounce the fork up and down, I don't hear it, everything works fine.

I seem to recall it always made such a noise if I raised the front end off the wheel to do work on the front.

Anybody hear a noise like this?

bountyhunter wrote:

...sometimes hear a kind of metallic noise that sounds like if you took a screwdriver shaft and tapped the fork tube...definitely coming from the front end down low...If I hold the front brake and bounce the fork up and down, I don't hear it, everything works fine...always made such a noise if I raised the front end off the wheel to do work on the front. Anybody hear a noise like this?

Not coming from the front brake caliper is it?

Wondering if possibly the dampeners on the floating part of the front brake caliper have become worn, which sometimes allows a clacking noise when rolling over road bumps, which noise disappears while the front brakes are applied.

Perhaps moving the forks allows the caliper to move so as to produce the mystery noise.

Good Luck!

I've tried holding the brake and rocking it front to rear, no sound. It is coming from the caliper area, so it's hard to say?

I'd check ft wheel bearings next G

With brake applied, caliper remains tightly in position, regardless of any slop in the floating action.

Am thinking the caliper "holder" attaches firmly to the fork and doesn't move during braking action, whereas the caliper attaches to the "holder" and floats in and out as the disks squeeze against the rotor.

Likely there are rubber dust seals and o-rings which dampen the caliper action as it floats back and forth.

The noise issue typically appears when a loose caliper (worn rubber dampers and o-rings, or metal part wear) clacks or rattles when the bike is ridden over tracks in a railroad crossing, or some other rough road surface. But the noise stops upon brake application, even while crossing the rough surface.

Without brake applied, is it possible to wiggle the caliper back and forth to feel any looseness or make any noise?

As an experiment, could remove calipers and attempt to replicate the noise under the otherwise same conditions.

Good Luck!

Patton wrote:

Without brake applied, is it possible to wiggle the caliper back and forth to feel any looseness or make any noise?

I'll try that tomorrow.