Final drive problem

Hi All,
This is a follow on to a post I made some time ago, basically I've got a nasty clunking/metallic noise when engaging drive - letting clutch out. With the bike,2006 GRiSO 1100, on a stand and in gear if I rotate the rear wheel there's a loud clunk when the free play stops. I found a post on the Wildgoose Forum which describes exactly what I'm suffering with (https://wildguzzi.com/forum/index.php?topic=74372.0), at the end of the post the guy says that he found the fault and it was a nut that was loose. Unfortunately the actual nut is not shown so I joined the forum and posted, one of the replies suggested it could have been the pinion shaft nut (the torque arm bushes are fine with no play), they also mentioned that Pete is the CARC expert so if he's around I'd be grateful for his input as well.
Many thanks in anticipation of some help as the bike is becoming difficult to ride.
Keep safe all.
Chris

First question is does the final drive howl, especially on the overrun? If not it is not the pinion nut having lost its preload so you can count that out.

Secondly, when you have the bike on a stand, in gear and with the motor off and rotate the wheel fore and aft that free play is the movement in the engagement dogs of the gear that is engaged and when it reaches one end or the other of its travel it will make a substantial clank. That is not unusual or worrying.

Having ruled out torque arm bushes my next questions are aimed at the gearbox itself. You say that this issue is becoming a problem that is impacting on how the bike rides? Can you elaborate on this please?

If you mean when you start to release the clutch from a standstill there is a sort of clattery noise and the take up, rather than being smooth becomes jerky at the same time the clatter occurs it is, unfortunately, likely that you have one of the early six speeds, (The year and model make it likely.) that have the inadequate shimming on the face cam shock absorber spring on the input shaft.

On these boxes on the input shaft there is a spring loaded face cam arrangement that, as shock loads are imposed, cause the face cams to run up each other. The shock is absorbed by the 'Spring' which is a stack of Bellville washers and once the shock loading has passed the 'Spring' releases allowing the face cams to run back down into their resting positions.

The problem with these early boxes is that for some reason, either the 'spring' collapsing due to the washers fatiguing or loosing their temper the face cams loose their preload to a point where they can *Rattle* against each other both at idle when the clutch is disengaged but also, more worryingly, as load is applied leading to the jerky drive engagement and nast clatter as the clutch is feathered.

Back in 2005/6 when the problem first appeared there was a recall and affected boxes were stripped and several extra shims put between the end of the spring seat to add preload to the shock absorber cams. This was only partially successful though and some boxes still 'Clattered' albeit to a lesser degree after the *Fix* was installed. My own belief is that this is simply down to insufficient shimming being added in the *Fix* and nowadays I'd be tempted to add enough that the shock absorber is almost locked solid! After all the 1200's don't have the wretched shock absorber in their gearboxes and they don't break! They don't bloody clatter either!

Now being 14 years old if you were to approach Piaggio about the recall you'd probably be able to hear them laughing in Pontadera if you stuck your head out of your bedroom window on a quiet night! You'll get no help from them! If though it is as I suspect the only fix is to open the gearbox and shim the spring tower.

Look. It may not be that but the three 'Commonest' things associated with driveline noise are those listed above. None of them are 'Common' per-se, final drive pinion nuts loosing their preload and wonky torque arm bushes were rare and generally speaking all the 'Nuovo Six Speed' gearboxes, with or without shock absorber, are bulletproof. The only *Known* issue with the early ones is the spring stack on those 2005/6 models and not all of them were affected, it was just 'Russian Roulette'.

Hi Pete,
Thanks for such a comprehensive reply, I'm really grateful. Got to love Guzzi always using the customer as the R&D department, don't know what I did wrong in a previous life but I still keep loving these Italian heart-breakers, previously had 1000S, 1100 Sport and V11 Sport.

The CARC box doesn't wine or howl so maybe it's not the pinion. The riding problem is when trying to use the bike around town, it's difficult to use the clutch with any finesse, it is snatchy and really does sound like a tractor. Maybe I'll have to just use it on sunny days and long country runs.

In your opinion based on experience etc, do you think the gearbox will be OK if I just leave it?

Cheers,

Chris

OK, now we are moving into other areas but to answer that question the answer is the company said that the noise would cause no harm. To which I say 'Bollocks'!

It's not the noise that is the problem but the fact that if the washer tower that forms the 'Spring' foreshortens enough the collets that's hold the whole sorry mess could pop out and then carnage ensues. This used to happen on the old five speeds that actually used a coiled spring rather than the Bellville washer tower. If the spring broke, which they do occasionally, the collets would get spat out into the spinning gears. The results were invariably catastrophic and sometimes lethal as the box tended to lock up as bits of collet jammed the gears and being downstream of the clutch when the rear wheel locked up deploying the clutch achieved nothing and a crash was almost inevitable.

Having said that I have not heard of that occurring on an early Nuovo Six Speed but it isn't beyond the bounds of possibility.

To return to your problem though I have to ask if it has been properly tuned? If you look at the throttle bodies is the paint still intact on the throttle stop screw on the LH throttlebody? Are there also un tampered paint marks on the linkage rod ball joints? Have you checked what the TPS reading is and has anybody tried to change the idle speed by turning the throttle stop screw in or out?

Being an early bike there is a very good chance that at some point in the last 14 years 'Harry Hometune' or a shaved ape at a 'Workshop' has decided to 'Fix it good' without understanding how the W5AM controller works and has fiddled with stuff that should of been left well alone!

How's yer toolbox? Do you have a manometer of some sort and a laptop with Guzzidiag working on it and cables to connect to the bike? If not then that's what you need to get to make sure that the tune is half way correct. Let's make sure it's running right so we can isolate if it is indeed the gearbox that is the source of the problem. Also does it have any modifications like silly air filters or loud, short muffler?

Oh, a couple of other, unlikely, possibilities are the centres ripping out of the clutch friction plates, (Although this is generally silent and is an 'All or nothing' sort of failure that happens quickly.) or one of the Hookes couplings in the driveshaft going tits and once again this is very, very rare on CARC bikes, even high mileage ones.

Certainly your problem needs investigating and unless you or the previous owner has done it I'd budget for new swingarm bearings and a shock linkage and wishbone as when you pull the swingarm it is likely those items will be toast.

It was I that told him to seek Pete, he know the CARC.

Yeah, thanks Steve. I saw his post there but I no longer contribute as I'm afraid I just got sick of being told I was wrong by the stupid. It was no longer worth the craic. Pity, as there are some good people on WG.

Why the fuck don't they do it for a living if they know so much.

That's the problem with the hive mind, too many drones who fancy themselves queens...