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CARC strip for bearing replacement.

An hour of my time or a possible bill for loadsamoney, no question in my book Pete.

It seems the one reported here in the UK (one careful lady owner) has buggered two bearings, so I guess the swarf from the nut thread got into those two pinion bearings.
 
Yesterday after descending a steep road in the mountains I noticed a potential issue with my 07 Griso. It seems that under slight acceleration or deceleration (basically light engine load, either braking or acceleration) I notice a kind of cracking sound/ knocking. If I increase the load, either buy rolling on or off the throttle it goes away. Could this be the wheel bearings in the CARC need replacing?

The history of the bike: purchased with 2400 miles on November 4th and now it has 3500. Any advice would be greatly appreciated and thank you for your time.
 
JDB said:
Yesterday after descending a steep road in the mountains I noticed a potential issue with my 07 Griso. It seems that under slight acceleration or deceleration (basically light engine load, either braking or acceleration) I notice a kind of cracking sound/ knocking. If I increase the load, either buy rolling on or off the throttle it goes away. Could this be the wheel bearings in the CARC need replacing?

The history of the bike: purchased with 2400 miles on November 4th and now it has 3500. Any advice would be greatly appreciated and thank you for your time.


What engine speed? If the engine speed was low it is most likely just transmission chatter. Cog it down one so the engine is spinning higher. While one can't say for certain It is highly unlikely to be a bearing problemb, especially at such a low mileage.

Pete
 
Pete, I will check that this afternoon. My worry is that after heavy engine braking in 1st and 2nd gear, introduced a measurable amount of slop..... I should have used the rear brake.

Your right the issue is at low rpm in higher the higher gears. I'll update after I test ride. Thanks.
 
Everything seems fine. Just over sensitive I guess. This bike was left outside so corrosion issues are a concern. I have spend several hours cleaning and checking the bike over. I need to learn about any preventative maintenance items that would be subject to corrosion especially in the CARC.
 
Pete, thanks for the posting - very informative. I have one question that you or someone else may have answered maybe I missed it. If the outer big bearing is is damaged does that indicate that the small in inner bearing needs replacing as well?

thanks
 
JDB said:
Pete, I will check that this afternoon. My worry is that after heavy engine braking in 1st and 2nd gear, introduced a measurable amount of slop..... I should have used the rear brake.

Really? I'm a heavy engine brake kind of guy. Not enough to chatter the rear wheel, but I've never worn out rear brake pads. Ever. I never dreamed that would harm the bike.
 
schimenator
It may not harm the bike, it will depend on how aggressive or ham fisted you are but it is a whole lot cheaper to replace brake pads than it is to rebuild or replace worn out drivelines.
Why hammer your clutch, gearbox and finaldrive (or chain and sprockets) to slow you down when brakes were designed specifically for this purpose and do it a whole lot better.

The same thing applies with cars and trucks.

Mark
 
Brake pads are cheap and easy to replace. That's not why I do it. I've never had a back brake that was any good. No feel. no stopping power. The Guzzi has the best rear brake I can remember on any of my bikes.
 
Mark111 said:
schimenator
It may not harm the bike, it will depend on how aggressive or ham fisted you are but it is a whole lot cheaper to replace brake pads than it is to rebuild or replace worn out drivelines.
Why hammer your clutch, gearbox and finaldrive (or chain and sprockets) to slow you down when brakes were designed specifically for this purpose and do it a whole lot better.

The same thing applies with cars and trucks.

Mark

The trick is to do it smoothly, in that case you're not hurting anything.
It also means that you'll always be in the right gear... Should you need to power out and change course quickly in the event of a sudden hazard. ;)
 
pete roper said:
Outer locking tang not bent up. Once the nut moves, (Not hard as the preload is retained simply by the nut torque which is miniscule and the locking tang on the outer edge of the washer.) the pinion will start to move about. Hammering forces will then destroy the threads on the nut and tear off the tang that goes into the slot on the pinion. Bye-Bye unit....

Pete
Thanks for the excellent information. I am into the carc on my '07 Norge to try and find an oil leak. I found the pinion nut locking tab to be engaged on the nut with a spot of green paint marking, but the nut was only hand tight, loose really. The seal runner ring under the washer was also loose enough to be able to be spun by hand which may be the reason for the leak? My question: What might be the torque spec for the nut? The washer and nut appear to be in good shape so I'm planning to re-use them when re-assembling. Any thoughts?

Regards,
Peter
 
I've done a few of my own loop and Tonti units which are still going strong after many years. I took another look at your photos of the stripping process and came to a couple conclusions. Appears I should hand tighten the nut, as there are no spacers between the inner races, then loosten to the next available locking tang, perhaps not unlike adjusting an old style automotive wheel bearing where tapered rollers were used. This as opposed to older bevel boxes in which there were shims between the inner races and therefore would require torque. Could this be because there is no pilot bearing on the nose of older style pinion? I was concerned that the rotation of the seal ring under the nut was a problem but after removing last night it appears the face that runs next to the inner race is polished and that provides the rings seal. This meathod was used on bevel Ducati twins at the counter shaft seal.

Peter
 
Part numbers for CARC service

I tried doing some searches for the cross-over part numbers, but the results were either incomplete or pointed me to a page from the old forum that is no longer where it once was. :?

From my research, I believe the required parts for a typical CARC service (mine is on a 2008 Norge) are:

Bearing seal MG part # 90408511 (85x110x8) or alternatively BMW part # 33121241938 (85x110x10).

Gasket MG part # 05358630 (if damaged).

Deep groove ball bearing 85x120x18 MG part # 92208518 or alternatively BMW part # 33121242210. This is likely the same as SKF 61917 or FAG 71917C, or others.

In general, no other parts are required (?)

Updates and corrections would be helpful, or if the original data has been missed in my searches let me know...

Thanks!
 
Re: Part numbers for CARC service

pyoungbl said:
Golly, we don't see too many CARC service topics. What's wrong with yours?

Peter Y.

Looks like the outer seal has a slight leak. No sign of bearing problems from the outside, but I wanted to get a handle on things before starting the work...
 
If the seal is leaking it's likely that there is movement at the large bearing. I'd recommend you change both the large bearing and the seal.

Check your old bearing I'd be interested to know if it is marked as a C3, if it is that's the wrong type, there's too much clearence built in to them, A C3 is designed for constant high speed use, like a fan on an electric motor where it's always running and at a high temp.

https://www.guzzitech.com/forum/topic?f=188&t=9974&start=10

Iain
 
I did replace the bearing (and seal) using the BMW parts; while I understand that preventive action on bearings may not be as useful here as in some other areas, the bike does have 70,000 miles and there were some suspect bearings in earlier bikes.

The old bearing is labeled as an NTN 6917C3.

Additional research indicates that this type has a small increase in internal clearance over a so-called 'normal' bearing of the same size. However, the reasons given for choosing to use a C3 are a bit more involved than the info in the link above. One key reason given in a discussion I found is that using oil rather than grease as the lubricant will give a higher running temperature for a given bearing - something that certainly applies here. Another reason has to do with how much the bearing will be compressed by the holder, apparently. Finally, the difference in internal clearances between a standard and a C3 bearing are very small - the 3 in the designation does not mean 3 steps up from C0, but just one. C2 is actually reduced internal clearance!

For wonks (like me) who want some interesting technical reading, just google 'why use c3 bearings'. Some other useful info is at:
NTN's FAQs - ntnamericas.com/en/product-s ... estions#f2
SKF's suffix list -
skf.com/group/products/bearings-units-housings/ball-bearings/principles/bearing-data-general/designations/supplementary-designations-suffixes/c/index.html
 
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