Gearbox knocking noise/ Vibration

[honda_biker]

I have an issue with my K75 1995. I recently did a gear oil change. I have used 75W-90 grade gear oil for this oil change. Unfortunately, I have been hearing weird "knocking noise" or "gear rubbing noise/vibration" at 70-90km/h speed band.

I spoken to a very experienced mechanic. He advised me to replace the gear oil with 85W-140 grade. Sad to say after this oil change, I can still hear some noise and vibration at 70-90km/h speed band.

Quiet when cold. Raps pretty hard when hot, goes quiet when pulling the clutch lever.

Can anyone give me a good advice or suggestion how can i resolve this issue??

Thank you very much.

[daveson]

How many km has your  brick clocked up?


How many knocks per second or seconds per knock, or does it vary?

Can you post a video of it?

Does this knock happen at 80km/h regardless of what gear you're in?

At coasting, acceleration, deceleration, downhill etc?

Also at 80km/h on centre stand? On centre stand, noise from engine, gearbox, final drive or?

You got a loose number plate somethin like that?

[Laitch]

I spoken to a very experienced mechanic. He advised me to replace the gear oil with 85W-140 grade. Sad to say after this oil change, I can still hear some noise and vibration at 70-90km/h speed band.

Can you post a video of it?

It's unlikely gear oil has anything to do with this. One possibility is that the clutch throw-out bearing and/or its spring could be faulty, especially if it's the cup-and-bearing style instead of the newer one-piece unit. Placing pressure on the assembly by means of squeezing the clutch lever might be what is reducing the noise. The vibration is probably coming from a different source or combination of sources, like tire wear, tire pressure, and/or front suspension needing cleaning and fresh fluid. Another possibility is the drive cushion assembly of the alternator. As daveson indicates, loose sheet metal could be a source, as could the clutch arm's touching the muffler enough to rattle. Check those out.

Hearing the noise could be helpful. Try posting a video of the noise on YouTube; make it publicly accessible then post its link here.