Sloppy/Slap LASH? in the rear end....?

The shaft final drive should have ZERO slop, and I'm sure it does, but what you guys are experiencing is slop in the transmission; listen carefully. It's normal to have some slop in the transmission, otherwise gears wouldn't engage. The problem is sometimes there's a bit too much. Both the GW and BMW use straight-cut gears, which are inherently noisier than helically-cut ones (keep that in mind), but are MUCH stronger, so durability is enhanced. By the way, a chain final drive has more slop than a shaft drive, because a chain HAS to have some slop, in addition to the tranny one. Just open and close the throttle in first gear (at LOW rpms) on both bikes, and it'll be immediately obvious there's more slop on the chain bike.
I experienced less noise in both my ex-GL1800 and BMW by switching to synthetic oils in final drive and engine (BMW has separate tranny fluid as well). I'm sure that should work on the Rune as well, but don't expect it to go away; straight-cut gears will always make noise (the typical tranny 'whine').

Finally, the slop is not going to hurt anything in the long run as long as it's not done constantly in a violent way (like when you close the throttle and reapply it abruptly, like to run a yellow light at the last moment; one more incentive NOT TO DO THAT). but it's certainly annoying. Low rpm amplifies that, so you can downshift a gear or two to alleviate the problem (as suggested earlier). I also used to anchor my right hand thumb to the throttle housing area on the GL to avoid jerking the throttle on broken pavement, which is almost impossible to prevent otherwise. Try that; works great.

Like most others here, I too have experienced "backlash" and recently adjusted throttle for less play. During a ride this evening, I thought the backlash was a little more pronounced. While riding on an open highway at about 70 mph, I accelerated slightly and as I remember, when letting off the throttle, I heard and felt a loud POP as though something had broken on the bike. I looked back for pieces of something that might have come off the bike or that I might have hit, immediately pulled off the road, parked the bike, got underneath; looked for some kind of damage; nothing found. After checking everything again, I turned around, circled back; literally looking for something I may have lost or might have hit. I again found nothing on the highway. Now I believe this was something internal in the transmission or shaft drive, possibly "gears" got in a bind or something. I am no mechanic, but this was a serious noise. I rode the bike to my house, about six miles, without any problems. This bike has about 3800 miles and has never been abused or even ridden hard. I am taking it to the dealership tomorrow for the 4000 mile service, and will certainly ask them to look into this; but I was wondering if anyone has an opinion as to what might have happened. I am very concerned that the bike might "lock up" while riding (?).

Lee (slydog)