Back in the day, adjusting your bike's chains was a chore that had to be done with annoying regularity. On a Pan or Knuckle, it takes about an hour or so to do the deed. You first have to loosen the transmission's four mounting nuts and one mounting bolt. Unfortunately, many a wrench has forgotten that one odd mounting bolt, which is over by the kicker cover, resulting in much distress and liberal amounts of verbal lubrication as he tries to get the still-bolted-to-the-frame transmission to move.
Once all the hardware is loosened, the transmission is slid back in the frame until the primary chain is properly adjusted. Once the transmission is again secured to the frame, you then loosen the rear axle and move the rear wheel to readjust the rear chain, since you screwed up its adjustment when you moved the transmission.
Once the chains are right, you have to readjust the rear brake rod, shifter rod, and, if equipped with a foot clutch, the clutch rod, because you changed their settings when you moved the transmission and rear wheel. Sounds like fun, eh?
Thankfully, it's not as bad for Shovelhead owners. Their primary chain has an adjuster inside the primary covers, so adjustments are a simple matter compared with the previously described procedure. Just remove the access cover, loosen the shoe bolt, move the shoe, tighten the bolt, and close the cover.
And though the rear chain must still be adjusted in a similar war, as on a Pan or Knuckle, it only gets adjusted as needed, since the transmission has not been moved for the primary chain.
In comparison, Evo and Twin Cam owners have a cakewalk. First off, there's no rear chain, just a check-it-once-in-awhile belt. As for the primary chain, it's adjusted the same as on a Shovel, which takes about 15 minutes to do. And, I guess, that's the problem. Seeing this normal bit of maintenance is no longer often required, owners tend to forget about the primary chain altogether. That is, until it's so loose it's slapping against the inside of the primary covers, doing its "the-engine-is-coming-apart" imitation.
The bucking at low throttle settings and hard shift that precede the slap dance are usually ignored or put up with because the owner thinks the fix to these annoying traits involves major transmission work.