I try to keep my bikes clean, and when I’m washing them, I pay special attention to those hard-to-reach places. But some places are totally unreachable, and dirt and grime accumulate, layer after layer, year after year.
On my 1977 Harley-Davidson Sportster XLH1000 “Ironhead,” one of these impossible-to-reach grime collectors is the inside of the primary chain guard. Normally I wouldn’t even think about the grime collecting there, but when I was freeing up a sticking rear brake line (which required some disassembly of the right primary cover), I happened to reach my finger around the back of the cover while trying to free the brake line, and my index fingertip sunk to the first knuckle in gritty, greasy grime.
I pulled off the cover to inspect it, and I saw that it was so deep, the chain was actually carving a groove through it. As I scraped away at it, the harder, deeper layers resisted until they gave away in big chunks. That greasy mess was slopped onto the primary cover sometime in the Carter administration.
It took about half an hour to clear out the grime, and while I was concerned the metal would be pitted with corrosion, the exposed metal actually gave off a nice dull shine.
Removing the primary cover wasn’t that big if a task, so I’m adding “Clean muck out of primary cover” to my 10,000 mile service checklist.