GRiSO 1100 Drive with metal fragments inside

That 'Piece' is the seal holder, but the part that the seal runs on is stuck in the seal. Stick your finger in from the back and pull the part the seal runs on out of the seal and you'll find another peg nut above it. My bet is the peg nut won't have any threads left in it.

I just looked and it's half past midnight in Austria! Go to sleep! Now! We'll continue this tomorrow morning your time!

true, thank you, i now understand how this works!
You are really great, thank you and good night from Austria!
[You must be registered and logged in to see this image.]

I am loving this step by step CARC servicing with detailed pictures and real time instructions from Australia to Austria . . .
Way beyond my mechanical abilities but bringing me a step closer to believing that, with proper guidance (and tools and time and space...! ) a numpty like I, could undertake such a task.
Gotta love this forum for such awesomeness. Thanks guys!

Hold on to your hat because we're about to get to some more critical and exacting stuff.

Havli wrote:

[You must be registered and logged in to see this image.]

Who is this child? He only looks about twelve! Far away from the usual GRiSO owning demographic who are generally older than dirt and have no hair on their heads apart from coming out of their nose and ears!

OK, before we go on to reassembly there are a few things we need to look at.

First. What actually happened here?

Well, the short version is that the pinion preload nut came loose.

The longer version is "Why?".

Well, the thing is neither the pinion or crownwheel bearings have a solid spacer between them to set the preload. That means that the nut can't just be cranked down 'Til you fart' tight because if you do it will a.) crush the rollers and b.) the friction created will cause a massive power drain and heat and the bearings will fail in short order.

To prevent that the nut can only be lightly tightened. Enough to, with the aid of the lockwasher, prevent it from undoing but not so tight that the frictional losses destroy the integrity of the bearings.

What can happen though is if the pinion bearings aren't seated properly on the shims and register in the neck of the reactive bridge on assembly, or if the bearings wear in time, the locking torque on the nut is lost and the only thing preventing it unwinding is the tabs on the lockwasher.

At that point the nut starts rocking too and fro and 'Chattering' on the threads. The eventual result is what you see above. The lockwasher disintegrates, the bearings loose their preload and eventually the threads in the nut, (Which is the sacrificial part.) disintegrate and it simply applies no preload to the bearings. The outer one lifts, the pinion cants over at an angle and the pinion destroys itself accompanied by a hideous howling noise on the over-run as you slow down.

Havli has been incredibly lucky in that his gears still appear to be good so we should be able to get him mobile again without too much cost or drama.

More later

A lesson in kinetic mechanics! Clear and thorough explanation of what happens inside the CARC when the pinion nut comes loose. I swear, reading it, I could see it all happen in slow motion and I‘ve never even been inside a CARC before.

Thanks Pete, keep’em coming!

Good morning guys!
Yesterday my posts were a bit overwhelming, so i will try to give you an short insight.

Regarding the thread of the nut, it seems to work, but its not at 100% anymore.
Will try to get a new one.
[You must be registered and logged in to see this image.]

The thread at the shaft looks good so far, no harm done.
[You must be registered and logged in to see this image.]

Regarding the preload of the roller-bearing i disassembled, now i know why it was a mistake.
But the good thing is, i can bring it back in its old position, because there are markers on it.
Its quite hard, but i think its doable.
[You must be registered and logged in to see this image.]

STOP RIGHT THERE!

It was hard and i almost sh*t in my pants, but the lockring is back in place.
I needed to hammer it in place, no chance with the hook-tool.
Lets hope it will last the next 200 years.
On Monday i will get the washer and also buy two new roller-bearings.

Anything i can do until then?

Sorry, I got tied up with other stuff yesterday afternoon. Let's get back to this.

Firstly, the crownwheel bearing locknut. Are you saying you had to tighten it with a hammer and punch? Sorry, but this sounds as if you will of applied far too much torque to it. Does the crownwheel still turn by hand? If not the loading on the bearings will be too high and they will fail in service. This is the reason it is best to not disturb the crownwheel bearings in any way unless there is obvious evidence of damage.

With both the crownwheel and pinion bearings, because the factory describes it as a non serviceable part there are no specified torque figures for the nut listed anywhere. I've not looked for a standard figure for the larger bearing size when used in this sort of application but for the pinion bearings, which are normally the only ones that need to be re-preloaded because it is the pinion lockwasher and bearing setup that fail the seeming industry standard is, for a 1 inch/25mm shaft, between 80 and 120 inch pounds of torque. That isn't very much! More and the bearings will gobble power, overheat and fail. Less and, once again, the nut will tend to loosen. I must stress how important it is to get this right.

The other thing is that both nuts for both crownwheel and pinion nuts should be Loctited using a high strength red or green Loctite. Why the factory, so fond of using it elsewhere, doesn't use it for these vital fasteners I have no idea? Speed and cheapness of assembly I expect. It's amazing that the factory seems to have a veritable Horn of Plenty when it comes to Loctite and use it on virtually everything nowadays but at the same time have a perennially empty grease pot! Enraging! But then they don't use Loctite on these vital fasteners!!!!

Now with the pinion nut and lockwasher sourcing these is even easier than seeking out a suitable well supplied SKF agent. Simply get in touch with one of the parts suppliers for older Guzzis, Teo Lamers, Agostinis, Stein Dinse or whoever and ask them for the nut and lockwasher that hold the front crank sprocket onto the crank on a model like a T3, SP 1000 or early LeMans 850. In fact just about any big block engine from 1974 through to the late 1980's. Yup, they are the same nut and lockwasher.

I also saw that in your picture above you had put the pinion nut on back to front. The chamfered side goes towards the dished spacer the seal runs on. This is to accomodate the dished shape of the lockwasher that goes beneath the nut and on top of the spacer. Note also the o-ring that goes outboard of the bearing between the inner race and the spacer. This is a crush-seal to prevent oil migrating up the pinion shaft from the interior of the bevelbox and should be replaced. Just take it to a bearing shop and ask for one, it's a common size.

In a case like this where the pinion has dumped it's preload as long as the gears are OK, and sadly they rarely are Havli has been really lucky, my advice is to do the absolute minimum to restore functionality of the box. That is, simply re-preload the bearings and Loctite the pinion nut. Don't even think about replacing any bearings as the deeper you get into the box the more difficult it becomes to get everything right again. I know, I've done it, but I have a lifetime of doing this shit and it still gives me the heebie-geebies! If you remove the pinion, which comes out with its support bearings leaving the depth engagement shims in the reactive bridge, it is practically impossible to get it back in without disassembling the crownwheel axle due to the caged needle rollers of the pinion nose support bearing tending to cant over and block the nose race's entry. The crownwheel has to be removed to allow you to hold the needles away from the pinion race. The whole thing is a fucking nightmare! It's doable. But believe me, it isn't fun!

All the bearings in the CARC bevelbox a HUGE the whole thing is monstrously over engineered. Oh they will wear out eventually, but not in our lifetimes! Anything that causes sufficient damage to require bearing replacement will of already trashed the gears and the entire unit will be scrap. With anything with CARC bevelboxes the less you do with them the better. Really.

Hi, first i have to say thank you!
Your Help is incredible, i am learning a lot

Yes, i tighten it with a hammer and a piece of steel.
I checked after every blow, if the crownwheel is still turning, in my view everything got a bit loose and is now hammered back in place.
If not, i will learn how to fix this after a longer ride

You are very thorough, i placed the nut indeed the wrong way around.

I will get all Parts and start putting everything together.

Thx and good night from Austria!

Good work. Once it is back together and on the bike take it out for a good ride and check the temperature of the box after 25 Km or so. If it's too hot to touch you have a problem.

I do strongly suggest you Loctite both peg nuts rather than simply relying on the lockwashers and would also say it is pretty much vital to replace both the lockwasher and the compromised pinion nut.

Sealing the two halves of the bevelbox case requires a sealant.I use Threebond 1211 but both Hondabond and Yamabond make decent alternatives.

Well done for fearlessly getting stuck in. I raise a tiny beer in your honour!

[You must be registered and logged in to see this image.]

Thank you Pete, you are awesome :-)

Nope. But I do like helping people. Especially those willing to throw themselves in and help themselves.

Just to keep you updated, parts are on its way, and i hope i can put everything together on Sunday.

I also worked a bit on "how to adjust the bearing play", which is indeed a difficult matter.

Not even sure if the standardvalues ​​are usable for this type of bearing, I think I'll tighten the locknut to 150N + Locktite.

I don't know whether the bearing clearance increases or decreases with temperature, as this has to do with the arrangement of the bearings.

The main wheel is definitely clamped very tightly, so i think the other one will be as well.

What are your experiences so far? Did you use a lot of force to tighten the nut, or rather very loosely?

No, no, no, no! Are you saying you've tightened it to 150 Newton Metres? Fuck me lonesome! No. You'll destroy the final drive in minutes!

The high torque figure is for the SEAL HOLDER! NOT THE RETAINER!

Not sure if i got your message right :-/

The KM08-Nut (the bigger one from the picture with the green positionmarks), i tightened with a hammer in order to get it in position.
I´m pretty sure we are talking about a lot of force, since i couldnt do it with the hook-tool.
But it turns and seem to work.

For the smaller nut, i didnt do anything so far, i´m just refering to the force i needed for the bigger locknut.
Just asking for a good quess of NM, in order to not have everything falling apart.

It's not a matter of falling apart. It's a matter of having too much force acting on the bearings.

Sorry, gotta go to sleep now. I'll continue this tomorrow, but relying on the original assembly marks is fraught with danger.

Instruct in Australia, spanner in Austria, but in realtime. Awesome, what a wonderful forum this is, thanks to both of you for sharing your knowledge and ongoing experience. Mon Chapeau

The big issue here s the lack of a solid spacer between the bearings on both the crownwheel axle and the pinion. If there was a spacer you could just crank down the torque like there was no tommorow just like you used to on the old Tonti pinion bearings.

The CARC system relies on a light preload being applied, just sufficient to, with the aid of the lockwasher, prevent the nut from loosening and unloading the bearings.

In reality the ideal situation would be that the bearings have zero clearance and no discernible preload. Similar to a simple trailer wheel bearing. The problem is that that sort of system the bearings are passive, they aren't really being asked to cope with any drive loadings so they can easily be retained by a stake nut or a castellated nut with a split pin to lock it! With the crownwheel and pinion bearings they are being asked to deal with 100 HP and 70+ ft/lbs of torque. Those sorts of forces would mince a split pin or indeed a lockwasher, as we have seen, if the nut, and therefore the bearings, loose their preload.

The problem we have here is that I have years of experience in this area and to be honest if I was tightening the crownwheel ring-nut I'd probably do it to an initial light torque of say 120-130 inch pounds but then I'd use my experience and judgement to add a bit more if I thought it necessary. From there it would simply be a matter of testing it and checking it's temperature and the condition of the oil. Remember, we have no instructions from the manufacturer on this so I'm working on 'Established engineering principle' rather than absolute 'Tablets of Stone, handed down from god'. I think we're doing something right though as I have a customer whose box Michael rebuilt fitted to his Norge that has done upward of 60,000kms now with zero problems!

Havli's biggest problem is lack of experience. The kicker is though he has nothing to loose. According to the gods at Mandello or Noale or wherever the box was designed it is a non serviceable item. In theory Havli should just chuck it away and get another one! Stupid, wasteful, unnecessary and of course expensive! Now while I would of preferred that he hadn't undone the crownwheel nut the thing is it has been done and so be it. If he attempts to re-fit it and does it up too tight, (Which is what I fear may be happening.) the worst that can happen is that it will destroy the bearings and then the gears. There will be plenty of warning of that happening though both with heat, (The centre of the casting with 'CARC' cast into it will get as hot as hades very quickly!) a significant loss of power, (That's where the heat comes from!) and noise! My guess is the bearings will howl like a bastard if they are grossly over torqued!

Ideally you want these nuts torqued to the bare minimum required to prevent them coming undone. You don't just tighten them down as far as you can. The loads on the bearings will be astronomical! That's how threads apply torque! Don't believe me? Go stick your finger in a vice and see how little torque you have to apply to the crank handle before your finger goes soft and squishy! It's not a lot!

Take the nut down until the bearings are seated. Then tighten just enough so that the nut is unlikely to loosen, with Loctite on the threads and then lend up whichever locking tab fits in whichever slot. It certainly wouldn't be more than 90* from seating the bearings. Do that with both crownwheel and pinion nuts. Make sure you can still turn the pinion by hand, reassemble the rest of the reactive bridge and assemble the bridge into the cases. Put it on the bike and test ride.

You may have to revisit it more than once, (We've not had to do so with any of the ones we've done.) but if you think about what you are trying to achieve and what you are trying to avoid it isn't beyond the Ken of mortal man or woman!

THX Pete!
Still waiting for my delivery, i will keep you informed about progress!

BR
Havli

Please do. It will either be one of success or a cautionary tale. I hope the former.

See, I like this. Ask for help. Receive help. Not just "do this" but WHY you do this.