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 Nasty CARC!

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Pete Roper
GRiSO Capo
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Pete Roper

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Join date : 2013-05-29
Age : 64

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PostSubject: Nasty CARC!   Nasty CARC! Icon_minitime1Sat Mar 20, 2021 8:31 pm

The bevelbox on the CARC system is generally pretty robust. The one Achilles Heel it has is the light preload on the pinion bearings supplied by the nut and the fact that it is held there simply by a lockwasher. For some bizarre reason Guzzi don't Loctite it and if the bearings settle or wear the preload is lost, the nut comes loose and things go pear shaped fairly quickly.

First symptom will be noise from the final drive on the over-run. If you notice this stop riding immediately. Not only could it preceed a catastrophic failure but also if you stop it there and then it may well be possible to save your final drive. I can't stress how important catching it early is.

If you don't and continue to ride the consequences may be terminal. Michael has just stripped Peter Hughes's box after he continued riding it for a while. Unfortunately it's fed bits of lockwasher all through everything and the results are terminal.

Sorry but there's no saving this one.

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

This is the pinion nose bearing. Most of the other bearings in the box and reactive bridge look much the same.

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

Now if you do catch it early and there is no crownwheel or pinion damage it is, despite what the factory may try to tell you, quite possible to rebuild the entire reactive bridge and therefore the bevelbox. My guess though is that very few shops would be willing to try it, either because they don't have anyone with the skills or for liability reasons. It's this sort of numbskull 'Built in obsolescence' that makes my blood boil and we won't have a bar of it. We can at least look at your box and tell if it's salvageable and if we can rebuild it you can bet your arse we'll be Loctiting the living Bejasus out of the pinion nut as it's preloaded so the bastard won't be coming undone again!

Oh, and as an indicator that this sort of repair is quite possible my box on my GRiSO played exactly the same trick. I caught it early, cleaned everything thoroughly and didn't even replace any of the support bearings! Just replaced the nut and lockwasher, Loctited and preloaded to about 120 inch pounds on the nut before bending up the tang on the new lockwasher. That was nearly 50,000km ago and it's still running silent and strong.


Last edited by Pete Roper on Sat Mar 20, 2021 10:14 pm; edited 1 time in total

Oz1200Guzzi, odder, lcjohnny, Mi_ka, Groovitz and Wolf like this post

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beetle
GRiSO Capo
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beetle

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Join date : 2013-09-30

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PostSubject: Re: Nasty CARC!   Nasty CARC! Icon_minitime1Sat Mar 20, 2021 8:51 pm


Arse!

&

cheers



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Duquois
Montanarolo
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Duquois

Posts : 24
Join date : 2014-01-24

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PostSubject: Re: Nasty CARC!   Nasty CARC! Icon_minitime1Tue Mar 30, 2021 12:13 am

Bloody Hell Pete, that is a timely message.
My GRiSO has recently started to rumble on the over-run.
It's in the garage now and I was about to investigate this weekend.
Thanks for the advice. Hopefully I'll be able to repair it.
Cheers, Andrew
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BowraBoy
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BowraBoy

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Join date : 2019-07-28

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PostSubject: Re: Nasty CARC!   Nasty CARC! Icon_minitime1Tue Mar 30, 2021 2:10 am

Displaying yet again my ignorance, can someone please explain the overrun to me and what it should sound like.
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Pete Roper
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Pete Roper

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PostSubject: Re: Nasty CARC!   Nasty CARC! Icon_minitime1Tue Mar 30, 2021 2:42 am

When you roll off the throttle and decelerate using engine braking.

As for sound? There should be no noticeable difference in noise when accelerating or decelerating. If you have an issue you will initially notice a slight noise when you roll off the throttle. Within a short period of time the noise on the over run will become a howl and/or a growl. This is bad.

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BowraBoy
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BowraBoy

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PostSubject: Re: Nasty CARC!   Nasty CARC! Icon_minitime1Tue Mar 30, 2021 4:10 am

Thanks for that Pete. I very much rely on engine braking, typically only using the rear brake when actually coming to a halt and the front brake very very little at all. All continues to sound good but thanks for alerting me (and all of us on the Forum) about this potentially nasty issue. Gertie has now done 90,000km - largely thanks to you and largely despite the local shaved ape, whose door I no longer darken!
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Dave Swanson
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Dave Swanson

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PostSubject: Re: Nasty CARC!   Nasty CARC! Icon_minitime1Tue Mar 30, 2021 6:17 am

Looks like a preemptive strike should be in order!
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jderienzo
Squinternotto
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jderienzo

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Join date : 2015-08-09

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PostSubject: Re: Nasty CARC!   Nasty CARC! Icon_minitime1Thu Apr 01, 2021 3:04 pm

Pete,

For those looking to accomplish the preventative maintenance, are you recommending your procedure be accomplished on #2 in the attached?[You must be registered and logged in to see this image.]


Last edited by jderienzo on Thu Apr 01, 2021 5:49 pm; edited 1 time in total
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Pete Roper
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Pete Roper

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PostSubject: Re: Nasty CARC!   Nasty CARC! Icon_minitime1Thu Apr 01, 2021 3:24 pm

Nope, that's the seal holder. The pinion nut isn't shown.

Probably the best bet as far as preventative maintenance is concerned would be to guide a few drops of Loctite 'super wick-in' down onto the threads of the pinion and nut through the opening in the seal carrier. Super wick in is actually built to be applied to tightened nuts and is supposed to wick down the threads. It sounds a bit implausible but Loctite make good products and have no need to bullshit.

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jderienzo
Squinternotto
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PostSubject: Re: Nasty CARC!   Nasty CARC! Icon_minitime1Thu Apr 01, 2021 5:48 pm

I like the wicking locktite idea better than the idea I had of tearing things apart!!!
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