Exhaust cracks...pipes and cans.
Thoroughly agree with all the slacken everything off before final alignment and tighten up; with some reservations!
The vibrations that you can feel running through the bike from time to time ( the slight to moderate one that all GS's generate) have to end some where and on the frame this will usually be where the engine mounts to the frame. So in this case we have a vibration frequency from the engine and another from the frame (road and transmission vibes) both meeting up at fairly hefty mounting points. These are strong enough to absorb the now colliding vibration frequencies.
Unfortunately in the case of the exhaust (after market stuff) the resonance in the exhaust note and the vibrations running through the front pipes, 'Y' piece and end can have very little paths through which to loose their vibrations.
The end can is kind of mounted flexibly, but that rear mount is quite hard and offers little by way of movement so vibrations have to be absorbed by the can. Results can be seen and are obvious by the cracking radiating out from the tail pipe (end cap) to the can edge.
Similarly with the 'Y' piece a whole host of vibrations are colliding at the centre of the Y and radiating around the middle.
The whole thing is magnified if the engine is slightly rough running or ridden very forcefully continually.
The catalytic convertor body would have been ideal for absorbing some or most of the vibrations as it has a very wide surface area over which to spread and loose the vibrations.
Now before anyone says 'piss off its all bollocks' go out and WITH GREAT CARE hold or feel the rear can/silencer with the engine running(leather/heat proof gloves would be good at this stage).
Feel around the 'Y' piece and you will see what I'm getting at.
The OE silencer is made of much sturdier stuff than the light weight Scremus and others and therfore, with its great weight and denser build, can absorb most of the harmful vibes that are causing the cracking problems some of you guys and girls are experiencing
You need to make sure that the rear can hanger bracket is flexible enough to allow it to absorb alot of the vibes meeting here.
CCM had a similar problem with their DRZ based bikes and with some of the older Rotax models, in a round about way I helped them sort that one out.
Please make sure that the exhuast is fitted by some one competent and then you should be ok. Scremus make good stuff as do many other manufacturers, I think these problem ones are probably either down to some Dealers poor fitting and other peoples hasty quick fits
I'll get me coat now then, got to polish me Aprilias x2, underseat exhausts, stainless pipes..modern...ish engine design etc etc.
)
IMO it should last longer than this.
