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CHECK THIS BOLT!!

John in PA

John in PA

Cruisin' Guzzisti
GT Contributor
Joined
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Location
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I was double-checking fit with the side case during Mistral exhaust install today and noticed that the main bolt which supports the CAT dead center behind the transmission was backed out around a half inch. That struck me as "odd." It also lacked the telltale yellow paint splash indicating recheck at the factory. I checked it (6mm allen and ratchet) and found that it was indeed loose. It screws into a blind threaded cast boss on the underside of the transmission case. This picture identifies the bolt, already tightened with as much torque as a prudent man would apply, and you can clearly see that the fastener is about 6mm too long for its intended job. (Rear of the bike is the left side of the pic, view from the right side of the bike

EDITED: LEAVING THIS POST HERE FOR CONTEXT, AND AS OTHERS MIGHT WONDER WHETHER THIS BOLT SHOULD *APPEAR* TO BE OVERLY LONG. CHECK YOURS ANYWAY ! THOUGH IT'S SUPPOSED TO BE LONG ENOUGH TO ALLOW FOR EXPANSION, MINE HAD INDEED VIBRATED LOOSE AND BACKED OUT AN ADDITIONAL 10-12 MM. CORRECT INFORMATION IN SUBSEQUENT POSTS.

I will be removing and replacing it after shortening it appropriately, but it clearly had vibrated about halfway out in just 200 miles or so of riding, so y'all might want to give yours a peep. (**This is the wrong solution!! see below for more information.**)

IMG_1989.webp
 
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Ugh… good that that you found that. I remember a post from a member named Pippen who had one of the early water hose clamp leaks. He took a lot of his bike apart looking for the source of the leak, and commented on some loose parts. I guess we ought to be on the lookout. Good luck!
 
Problem solved. Fishing through the multi-drawer cabinets on the "Pegboard of Orphaned Guzzi Parts," I found a machined aluminum bushing just the right diameter and thickness (0.300") to allow proper torque on the bolt without bottoming in the casting. Easier that cutting and cleaning up the threads on that hardened bolt.
Done!
Now, I wonder what other surprises await...

NOTE: THIS WAS THE INCORRECT THING TO DO!! FURTHER INFORMATION FOLLOWS IN SUBSEQUENT POSTS, THIS THREAD.
:rolleyes::eek:
 
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You shouldn't have done it. All Mandellos have long such bolt, it is done that way to allow thermal expansion of the exhaust where catalytic converter will generate much heat.
 
santuz said:
You shouldn't have done it. All Mandellos have long such bolt, it is done that way to allow thermal expansion of the exhaust where catalytic converter will generate much heat.
Click to expand...
Exactly, a lot of exhaust systems have such a long bolts for a purpose.
 
santuz said:
You shouldn't have done it. All Mandellos have long such bolt, it is done that way to allow thermal expansion of the exhaust where catalytic converter will generate much heat.
Click to expand...
Jan Cermak said:
Exactly, a lot of exhaust systems have such a long bolts for a purpose.
Click to expand...

OK, I'll bite.

What should John have done?

Bill
 
The bolt had backed out at least a half inch in 200 miles riding. There is a rubber (silicone??) bushing mount with a steel inner bushing to prevent over-tightening. Doesn't the rubber bushing provide for vibration and expansion needs?
 
John in PA said:
I stand corrected!! Found this in the service manual. Torque 25Nm and hope for the best!! :rolleyes:
Click to expand...
Fascinating! So, maybe your bolt wasn’t “loose” after all? That’s what worried me. Ride on!😁
 
My $.02… IF I kept that heater box in place, I’d use a treaded stud into the casting with thread-locker, and double nut the end. 10mm seems excessive! Also destined for demise IMO.
On “race” systems, this mounting point is not needed and is problematic if used in my experience.
 
The bolt to check is the one that connect the muffler to the passenger footpeg. I heard couple of Mandellos that had the bolt loose and if you don't tighten, weight and vibrations can crack the exhaust pipe.

Luckily mine was well tightened :)
 
GTM® said:
My $.02… IF I kept that heater box in place, I’d use a treaded stud into the casting with thread-locker, and double nut the end. 10mm seems excessive! Also destined for demise IMO.
On “race” systems, this mounting point is not needed and is problematic if used in my experience.
Click to expand...
“IF” … I like that😁.
 
BDS said:
Fascinating! So, maybe your bolt wasn’t “loose” after all? That’s what worried me. Ride on!😁
Click to expand...
No, it had vibrated out at least 10-12mm further. That's what caught my eye in the first place. And the CAT is quite heavy. When removing/replacing the bolt, a padded scissor jack is necessary if you're doing it solo like I did.
 
Here is a picture of mine , my dealer has said don't touch it , and they will look at it when they take it in , but I had the same discussion on a FB page and everyone's else's seem's the same .
 
There is a tech bulletin from February that discusses this bolt as well. Tighten it, but dont shim ths gap!
 
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