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 Silent Bloc

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Posts : 713
Join date : 2021-07-30
Age : 61

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PostSubject: Silent Bloc   Silent Bloc Icon_minitime1Thu Nov 04, 2021 4:06 pm

So not having the original GRiSO Torque Arm (Rossopuro) found two 4mmX18mm O-rings mounted on two seperate side plate bushes.
These compared to new ones had lost their elasticity.
Potentially they had maybe lost a little bit of width or were crushed.
Being crushed the side of the bush/side plate the O-rings fit to was grating on the actual arm as pictured. Causing rattles squeaks and wear damage.
Silent bloc pictured for comparison.

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Decided to try out some 5mmX18mm viton O-rings, these babies look huge in comparison yet fit the recess of my side bush mounts almost precisely.
I did add a little rubber grease to aid them fitting and movement (up and down).
I notice you can over tighten the mounting bolt effectively crushing said O-rings, pretty obvious really.
It's got a locknut in theory it should never work itself undone.
The original GRiSO bush is superior in this regard to the Rossopuro as pressure is only added to the metal bush.

My bike with these fitted is once again pure, can you imagine what it was like test riding prior to purchase, I heard this dreadful clattering and squeaking.
The owner was in complete denial, I knew it wasnt gearbox or engine related, so progressed with the purchase.
Asking on this group amounted to nothing useful though the information was on here it was diluted and vague.
Steak saved my aggravation with his mention of Stucchi when enquiring about grab handles on his previous 1100, this in turn led to the Silent Bloc and there after coupled with Guzzi Steves mention of symptoms on a previous post my curiousness of it led me to solving the bikes extra noise issues Very Happy

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So the Carc moves up and down, at the front this is greatly reduced but still it does move some.
So considering the original GRiSO torque arm bush this greased had movement capabilities.
Two fat greased seals/recessed making the bush, held in a cage inserted into the torque arm.

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The so called update the Silent Bloc's only movment if the mounting bolt is wanged up tight is the actual Rubber/Polyurethane its made up of tortionally flexing up and down.
The outside of the Silent Bloc over taking the inside mount.
If its not tight the centre mount will potentially eat away at the side plates.
Originally these (silent bloc) are vibration dampers.
Sounds to me like a recipe for destruction and the mounting plates being treated to similar as the metal centre of the Silent block potentially erodes at the side plates?
Probably an exaggeration on my part, or I've over thought it which I regularly do, but surely if the resistance to flexing (wanting to return to normal) is very strong on the part of the silent bloc this in turn might have an effect on damping rates?

My unfounded opinion is stick with the original pre silent bloc mount, occassionally grease o-rings or replace them and carry on. No worn sideplate mounts.
I heard that new arms come from the factory with the silent bloc already in place should you buy a replacement, in the which case I guess you shit out  Laughing
Easy to see the original bush has a large flat outer compared to the silent bloc nasty little centre.
The Rossopuro torque arm mount is a copy of the original done different.
It allows the arm to move/slide up and down if greased, being viton its resistant to the grease causing damage to the O-ring, the mounting bolt doesnt need to be super tight and the O-rings take up the side to side slack.
First sign of a rattle replace the viton O-rings £2.30 a pair.
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