Guzzi clutch noise and wear

[Chuck]

(posted by docc in "Sticking clutch")

 

 I've held the clutch in at stops all these years

Well, at least you've learned not to do that..

[luhbo]

Why is it so bad for the clutch if you hold it in at stops? At least for the input gear this should make life much easier. For the friction plates it should make no difference. Even the pressure plate as well as the other one, which I right now can't name in you lingo, would normaly have some benefit from being able to rattle independly from each other and free from the masses of f-disks and gearbox parts. The only part having hard times would be the small axial needle bearing, but that is what it's made for.

 

Last, but not least, when you hold in the clutch, all the usual hammering comes to a halt. This could be a good sign,too, I think.

[Chuck]

I think from the uneven firing impulses. The two clutch plates and intermediate plate are free to rattle back and forth. IIRC, Pete explained that one time.

[luhbo]

They rattle anyway, just with the whole lump of gearbox etc. behind them. And always into the same groove. Pull in and they get lighter and hammer on different points. Make a sketch.

 

 

BTW, you remember the days, when every honnest Guzzi rider had to bore the end drive cushions, or better even get rid of half of them? Or when motor braking was deadly sinn No 1? Or when it was a definite must to add a diode to the Reg harness, otherwise you'd definitely end with a dead battery (just as a side note)?

The cushions, IIRC their hardness was the problem. They didn't kill directly the battery but sooner or later for sure the rest of the bike. I think someone even started a 'Comfy Cushions' sourcing campaign. Others made a sketch of it,too. Some years earlier, way ahead of their times obviously

[Chuck]

How do they rattle with spring pressure against them?

[luhbo]

All parts that can be moved or shifted relativ to each other must have some play between them. That's why and where they rattle. The torque goes over the teeth, not over the springs.

[Chuck]

All parts that can be moved or shifted relativ to each other must have some play between them. That's why and where they rattle. The torque goes over the teeth, not over the springs.

I'm not buying that. There's no play between the clutch plates and intermediate plate when the clutch is released.

[Chuck]

(posted by Andy York in "Sticking clutch" http://www.v11lemans.com/forums/index.php?showtopic=20037&p=223037)

 . . . clutch plates hitting side to side -- if sitting at a red light with the clutch pulled in...bang bang bang.

if you sitting there in neutral, idling, not much going on  . . . 

Uhh, yeah. That's what I've been saying. 

[luhbo]

 

All parts that can be moved or shifted relativ to each other must have some play between them. That's why and where they rattle. The torque goes over the teeth, not over the springs.

I'm not buying that. There's no play between the clutch plates and intermediate plate when the clutch is released.

Have you ever seen any wear between clutch- and intermediate plates?

Make a sketch of the torque path through the clutch, from the crankshaft to the gearbox input shaft. Mark where the play is and compare this with the pix posted.

 

Also worth a thought: people hold in the clutch because they keep in the first gear. So obviously the entire lower half of the drivetrain stands still. From rear wheel to the clutch disks. No movement, no wear.

[Chuck]

 

 

 So obviously the entire lower half of the drivetrain stands still. From rear wheel to the clutch disks. No movement, no wear. 

The way I see it is from the rear wheel to the input gear on the transmission. None of that is turning because the pressure plate pressure is relieved and the two clutch plates and intermediate plate are free to rattle back and forth with the lever pulled in. Once the clutch lever is released, the springs push the two clutch plates and the intermediate plate together, and the clutch plates drive the transmission input gear. If the transmission is in neutral, the transmission input gear is being turned by the clutch plates, but none of the gears are engaged.

[docc]

Discussion moved here for clarity of both threads and better enjoyment by all of the enthusiastic participants and readers.

[luhbo]

... and the two clutch plates and intermediate plate are free to rattle back and forth with the lever pulled in. ...

 

 I didn't think of the back and forth DOF. But is this axis a problem? The engine pulses in another plane, and the wear we see on the splines surely comes from the radial rattle. Back and forth would be axial.

Anyhow, I see a good chance that holding in the clutch at stops in 1st gear or at other occasions isn't really that bad, maybe more weal than woe even.

 

Really bad for the clutch and the splines is probably being hard on the throttle at lower revs, let's say below 3 or maybe 4k.

And then, Docc's V11 has seen some miles, why should the parts look as new?  The usual life span of a motorcycle is below 50.000, everything above is a bonus for the owner and lost profit for the manufacturer. See it this way.

[swooshdave]

How do they rattle with spring pressure against them?

 

No spring pressure as the pressure plate has been lifted.

[docc]

 

... and the two clutch plates and intermediate plate are free to rattle back and forth with the lever pulled in. ...

 

 I didn't think of the back and forth DOF. But is this axis a problem? The engine pulses in another plane, and the wear we see on the splines surely comes from the radial rattle. Back and forth would be axial.

Anyhow, I see a good chance that holding in the clutch at stops in 1st gear or at other occasions isn't really that bad, maybe more weal than woe even.

 

Really bad for the clutch and the splines is probably being hard on the throttle at lower revs, let's say below 3 or maybe 4k.

And then, Docc's V11 has seen some miles, why should the parts look as new?  The usual life span of a motorcycle is below 50.000, everything above is a bonus for the owner and lost profit for the manufacturer. See it this way.

 

I expected my flywheel to look much worse at 99,000 miles. I did not expect the input hub to look so bad, but no one expected it to come completely loose, either. (That was certainly my increasing idle rattle noise.)

 

While I am not one to run the Sport below 4,000 RPM, I am admittedly often hard on the throttle and downshifting/ rev-matching, then hard on it right back up again.  "Hell-on-wheels!"  . . . and tires . . . and brakes . . . and clutches . . .

[Scud]

Good technical discussion.

 

The way I see it, noise = wear. So if you hear noise, you think about what is wearing.

 

When the clutch lever is in (for a standard dual plate clutch), then the following parts can rattle around inside the flywheel:  two friction plates, one intermediate plate, and to a lesser extent, one pressure plate. I say to a lesser extent on the pressure plate because it is not totally free due to the extra compression on the springs. There are several areas of potential impact - the outer gears of the pressure plate and intermediate plate against the flywheel, the inner gears of the friction discs against the transmission input hub, and all the loose plates against each other.

 

When the clutch lever is released, everything snugs up and moves as one unit - no impact, no noise, no clutch wear.

 

Then we have the question of what is spinning. When the clutch lever is in, the tiny throwout bearing carries the load of all 10 clutch springs. When the clutch lever is out (and transmission in neutral) the engine's power just goes the main transmission shaft, which is carried by two massive roller-bearings.

 

IMO, keeping the clutch pulled in a idle does three bad things - increase wear on the clutch, increase strain on the throwout bearing, prolong the strain on the seals in master and slave cylinders. I think that letting the main transmission shaft spin at idle (in neutral) is a non-event. That shaft spins full time when the bike is in motion. A clutch is designed for short-duration use - a transmission for continuous-use.

 

Perhaps we can have another discussion about why single-plate clutches are noisy when the lever is released, and quiet down when the lever is pulled in.