Clutch knocking sound

Hi all. Seeking some general advice if I may.

Had the GRiSO serviced recently, and did all all oils/fluids, including gearbox oil etc. Since this time, I've noticed that on cold starts in particular, the clutch is making quite a knocking sound that's clearly audible over & above the usual valve-train clattering. This only happens with the clutch engaged (i.e. lever out). As soon as I pull the clutch lever in, the sound disappears entirely. Once warm, the noise is a lot less noticeable.

Just wondering if perhaps different oils may affect how "noisy" the GRiSO clutch is, or whether it has nothing to do with oil at all. Been a few cold mornings in Melbourne recently, and perhaps this contributes a bit too. I just never recall it as being so noticeable prior to getting the bike serviced. Just hoping that it's not a telltale sign of something about to detonate.

Brent.

No it's not. Beer with me for a few hours and I'll explain the likely cause.

Pete

Would be nice to share this with other members. I have the same issue. The dealer said this is no reason to be worried and my GRiSO is not alone with this. The issue may also affect replaced clutches.

Pete Roper wrote:

No it's not. Beer with me for a few hours and I'll explain the likely cause.

Pete

I'll have a beer with you Pete while waiting for your reply

"My clutch is making a funny noise! Oh woe is me!" (Cue rending of cloth and throwing of ashes!) "It's about to fail and cause the end of civilization as we know it!" (About this point wee starts escaping and an Internet myth is born.)

Alright. Now a bit of data and evidence.

Whenever anything goes wrong on anything nowadays in the age of the internet the first thug the monumentally aggrieved because their lives aren't perfect do is go online and whinge. This can be everything from their airliner crashing to their coffee being the wrong temperature because their favourite barista has a fucking hangover!

So let's get down and dirty with Guzzi clutches.

Essentially they are fairly bulletproof. Sure, because they are bought from the cheapest supplier you can tell that they are built to pretty much the lowest acceptable standard but on the whole all of them, from the old twin plater used on the 2VPC models through to the single plate variants used on the 8V's and smallblocks, are pretty reliable.

Sure, there are exceptions. In 2012 there was a seriously poxy set of friction plates in a short run of 8V's, as far as I know all of them were Stelvios. In the late nineties there was a run of really poxy friction plates that went into Cali 1100's and a few V11's and there was the horror story of the Scura single plater and the early Hydro Cali single plater in the 2003-4 period. Generally though, when compared to other marques problems these were rare, it's just they got talked about more because Guzzi owners, especially the Corn Cob Pipe mob are as verbose as fuck and have forgotten that the 'Old Bikes' were nowhere as good or reliable as they remember!

So, getting on to why your 'Clutch' on your 8V is 'Knocking' the simple fact is it isn't!

The entire assembly on the 8V is fairly light. As the motor fires the crank accelerates and decelerates unevenly due to the firing sequence. The lighter the rotating mass connected to it, (Including not only the crank but the flywheel/clutch and the alternator belt and armature as well.) the less mass there is to act as a kinettic 'Battery' to store energy and even out the power pulses.

When the clutch is disengaged, (Lever out.) the input shaft in the gearbox is also accelerating and decelerating with the crank etc. Unfortunately the secondary shaft and the output shaft pinions have no incentive to do the speed up/slow down thing! All they want to do is sit bloody still!

So every time the input shaft speeds up it speeds up the input shaft and primary gear and then as it slows down the primary wants to keep spinning so the backlash in between the pinion teeth is smashed back and forth and it makes a knocking noise! It's NOT the clutch! Engage the clutch and the noise goes away beacause the input shaft, (Especially on a new bike where the seals on the 2RS bearings in the gearbox are still tight!) will slow to a halt or at least not have the power pulses to cause the hammering.

This can also be exacerbated if the throttle body balance is out or the idle speed is too low. There is a reason why the target idle, (Several actually!) is 1250 +/-50 RPM!

As suggested, on new, *Tight* bikes the issue will be more pronounced. By the time I swapped out my original box, (Not because it was in any way bad, simply I had a virtually new on with my new engine.) everything inside it was so sloppy and *Loose* knocking at idle was a total non-issue!

Will your clutch fail? How the hell would I know? You might ride like a complete dingbat! You might have zero mechanical sympathy and a sense of entitlement that says if it breaks it's not your fault even though you are a mouth breathing retard with the fine motor skills of a sea anemone on crack! You might even just get unlucky! The chances of the latter though are really quite remote.

Don't fret unduly but DO ensure the TB's are balanced and idiots haven't buggered about with stuff they shouldn't have on the TB's as that will simply make the knocking worse.

Pete

Um, ok. Thanks Pete. Not entirely sure that I'm glad I asked, but I get the point I understand the mechanical aspect a bit more. I think my idle speed may be a tad low too which would contribute.

So, if the gearbox oil was recently changed for something quite thin, technical term, that would result in more rattle or 'knock' at idle.

Brent S wrote:

Um, ok. Thanks Pete. Not entirely sure that I'm glad I asked, but I get the point   I understand the mechanical aspect a bit more. I think my idle speed may be a tad low too which would contribute.

Idle speed is hard coded into the ECU. I didn't think it could be changed but a Mark has disabused me of that notion but it has to be done with Tunerpro or similar at the map building level.

The thing is though that whatever the target idle speed, as long as the stepper motor is working correctly and the throttle bodies haven't been messed with it will be achieved, or very close to it. On the 1200's it's 1250+/- 50 rpm. If it isn't? Either the stepper isn't working or someone who doesn't understand has set the bike up wrong.

Pete

Brent S wrote:

Um, ok. Thanks Pete. Not entirely sure that I'm glad I asked, but I get the point   I understand the mechanical aspect a bit more. I think my idle speed may be a tad low too which would contribute.

Well, I am glad you asked, Brent!  

Seriously, quintessential Pete Roper teaching us in his inimitable style.

[Thanks, Pete.]

Bill

P.S.  In Atlanta (on Norge) after 2000 miles in Va., W.V., Md., Pa., N.Y., Oh., Ky., Tenn., and now Ga.  Was with a Florida friend on his 8v Norge my brother once owned.  I only mention this because if those machines had run any better or given more joy we'd need to check in to a detox facility.  What a grand time.  And, two more days ahead back home to Cross Junction. Life is good.

Nobleswood wrote:

So, if the gearbox oil was recently changed for something quite thin, technical term, that would result in more rattle or 'knock' at idle.

In theory? Yes, until operating temperature is reached after which unless the upper VR was much higher than the recommended it would make no real difference.

Pete

My bike does that since new and I figured it had to do with input shafts and all...
Besides, anything Italian is noisy. lol

Great response, Pete. Like Bill, I'm glad he asked. The thing I was surprised you didn't mention is the sacred screw, and not to fuck with it in the belief that idle speed can be adjusted that way.

I believe that has been covered adequately by now, I, and others, have railed on about it a dozen times!

What still worries and depresses me is that the W5AM system used on our bikes has been around on Guzzis since 2005! It has to be one of the simplest, most foolproof, systems ever used with the one caveat that it is still possible to arse about with the 'Sacred Screw' and you can bet dollars to donuts that Harry Hometune will do just that! The worrying thing is that I'm still seeing bikes that have been serviced by 'Authorised Guzzi Dealers' coming through now, thirteen years on, that have either been tampered with inappropriately or alternatively never touched at all!

Another common one is finding both the air bleeds open one and a half turns. Why? Because that's where carburettor idle mixture screws are *ideally* set! ! God give me strength!

Pete

PS. Brett, my original response was in no way supposed to be a criticism of you or your question if you took it that way.