First Gen 1200's
...seem to have a DESIGN flaw.
I was having chain wear issues...only getting 5-8000 miles on a chain. There was also a lot of sprocket-chain CLATTERING noise, especially at the rear sprocket.
I tried a few things... finally discovered:
1) the chain adjustment marks were off by ONE FULL MARK. (I used a Motion Pro chain alignment tool to find this).
2) there is an inherent weakness in the rear axle assembly line-up... the SPACER that sits inside the sprocket carrier, fits between the inner wheel bearing and the outer wheel spacer (left side) gets PUMMELED, especially when the alignment marks are not perfect. the END FACE looks like someone hit it with a flat hammer repeatedly.
What this ends up doing is allowing a WOBBLE in the whole carrier, even when the axle is tightened down. So, when the chain is yanked forward, the entire sprocket will PULL to one side, causing a front to rear sprocket mis-alignment... causes a clattering noise (the chain wants to hang-up going over the front sprocket)... and you'll get excessive wear on one side of the sprocket only... and the chain won't last so long.
The reason I know this is a factory design flaw is because they CHANGED the rear carrier..and spacer.. on the 2nd Gen GSF's.
Keep an eye out for this when you change your tires: pull the carrier off the wheel hub (you should replace those rubber biscuits regularly anyway), and pull that center spacer out... look for signs the end has flat denting.
I'm bypassing all this by replacing EVERYTHING in the swingarm area.. including the swingarm.. with 2nd Gen parts: anything that changed part number, I'm swapping it out. Hopefully, this will give me all the benefits of the 2nd Gen factory design improvements.
But short of that, just make sure your rear sprocket carrier isn't LOOSE: grab it at three o'clock and nine o'clock and try to wobble it in and out. If you get PLAY, you'll now know why.