Silencer heat shield hardware strangeness

[mattsz]

I started my bike today and heard a faint clattering sound - quickly chased it to the shield on the silencer.  One of the three hex-head screws securing it was gone.  I went to the hardware store with allen wrench in hand (pocket, actually), and removed a second screw to find a match.  It came out with little difficulty, with threads slightly surface-rusty but otherwise intact.  The shortest replacement I could find was just a hair longer than the original.

I put both back on the bike (they both went on fairly easily), and sure enough, the longer screw bottomed out just before the head clamped down on the shield.  I thought I'd grab a washer to fill the gap, but...  darned if I could get either screw back out again.  After I got home, I waited for things to cool down a bit, then went after both screws with penetrating oil, all the while thinking I was going to strip the hex socket or break the tool (not likely to break the head off the 6mm screw).  I eventually got them both out, with threads intact,  but what the heck is going on here?  I was going to lock-tite them, but now everything is saturated with penetrating oil.  Anyway, I don't see how they would have come out on their own as tight as they were.

Ideas?

Will residual penetrating oil bother blue lock-tite?  Will blue lock-tite work at all with the heat of the exhaust?

[Ducati Scotty]

Heat promotes oxidation.  Thing that get hot rust faster, simple as that.

I threw those silly little allen head screws away the first time I got them out.  I replaced them with standard hex head bolts in stainless steel.  I had to cut them down a bit but that was easy enough with a Dremel.  Now when I need to take them out past the accumulated rust I know I can get enough torque to do it.

The residual oil will block Loc-Tite.  Just use some solvent and a Qtip to clean them out.  At those temps no LocTite is going to hold BUT it will fill the gap with it's plasticky-ness and help prevent more rust.

Scott

[barenekd]

The Loctite will work, but a better plan is to get a different muffler. I had the same problem with my stock muffler the day I picked it up. I heard the rattling but kinda dismissed it, and a few weeks later, got an EFI muffler and when removing the bazooka, found the heat shield screws loose.
Bare 

[mattsz]

My Boys!!!   

Thanks guys!  I think I would like to replace the bazooka with an EFI, but I don't want the bike to be any louder.  Anyway, that will probably be next season's "project".

Solvent: Alcohol?  Acetone?  Mineral Spirits?  (That's all the solvents I have...)

[Bulletman]

My Boys!!!   

Thanks guys!  I think I would like to replace the bazooka with an EFI, but I don't want the bike to be any louder.  Anyway, that will probably be next season's "project".

Solvent: Alcohol?  Acetone?  Mineral Spirits?  (That's all the solvents I have...)

Mattsz, I would enjoy a drink while doing it... Alcohol works really well.. 

[Ducati Scotty]

Acetone would work fine.  You just need something that will cut the oil.

Scott

[Arizoni]

I doubt that Loc-Tite will last in that area of the muffler.
Based on the colors of the chrome plating I would guess it could get well over 700 degrees F.
A heavy split lock washer would probably do a better job of securing the screws.

[Ducati Scotty]

Yeah, but it can't hurt either.

Scott

[gremlin]

Heat promotes oxidation.  Thing that get hot rust faster, simple as that.

+1

[mattsz]

A heavy split lock washer would probably do a better job of securing the screws.

... and, the washer might just be thick enough so I don't have to shorten the screws...