The bike is a mostly stock '81 XS400-SH with 7500 miles (had it since 1900 miles around 6 years ago. It's fairly beat-up, but been a solid bike for getting around for several years now. It runs just fine. I use it frequently now because getting parking on campus in the daytime is impossible. I'm running a one tooth bigger front sprocket, and XS650 shocks for more comfort on my commute at 60+ mph.
I recently put on a new set of Duro tires (same size and everything that I previously ran for 5000+ miles and corded), and went ahead and tightened the chain to spec at the same time and made sure it was running straight (never paid much attention to that before). It ran perfectly well for around 15 miles, then I felt a vibration that made me uneasy. I pulled over and checked axle nuts and anything I had recently reassembled, and all looked OK. I suspected maybe I lost one of the new wheel weights, so I took the wheels to a different shop, and they said they were perfectly balanced.
Neck bearings seem OK, wheel bearings feel OK, rear swingarm bushing is greased. Chain had been rather dirty and stiff, so I took it off and cleaned it thoroughly and lubed it up. I changed rear brake assembly too (I boogered up threads on a lever arm before, and just got a different assembly and shoes on ebay).
Still, either I'm just paranoid, or it feels shaky. I can't track it to a certain RPM or speed, but it does gradually increase until around 55mph, and at 65mph it starts to get less noticeable.
I can't pinpoint it to front or rear. I can feel it slightly through my handlebars, seat, and footpegs.
Any ideas what else to check? It almost feels like its something unbalanced in the engine itself, but it doesn't seem to be at just one RPM.
I'm wondering if some imperfections on the surface of the tires just need to be worn off, but my last set never had this problem, and its weird it just started 15 miles after putting them on.
I've thought about loosening up the chain a bunch to see if it helps, but that doesn't seem proper, and the cleaning/lubing it didn't seem to affect it.
Thanks for any help!
I recently put on a new set of Duro tires (same size and everything that I previously ran for 5000+ miles and corded), and went ahead and tightened the chain to spec at the same time and made sure it was running straight (never paid much attention to that before). It ran perfectly well for around 15 miles, then I felt a vibration that made me uneasy. I pulled over and checked axle nuts and anything I had recently reassembled, and all looked OK. I suspected maybe I lost one of the new wheel weights, so I took the wheels to a different shop, and they said they were perfectly balanced.
Neck bearings seem OK, wheel bearings feel OK, rear swingarm bushing is greased. Chain had been rather dirty and stiff, so I took it off and cleaned it thoroughly and lubed it up. I changed rear brake assembly too (I boogered up threads on a lever arm before, and just got a different assembly and shoes on ebay).
Still, either I'm just paranoid, or it feels shaky. I can't track it to a certain RPM or speed, but it does gradually increase until around 55mph, and at 65mph it starts to get less noticeable.
I can't pinpoint it to front or rear. I can feel it slightly through my handlebars, seat, and footpegs.
Any ideas what else to check? It almost feels like its something unbalanced in the engine itself, but it doesn't seem to be at just one RPM.
I'm wondering if some imperfections on the surface of the tires just need to be worn off, but my last set never had this problem, and its weird it just started 15 miles after putting them on.
I've thought about loosening up the chain a bunch to see if it helps, but that doesn't seem proper, and the cleaning/lubing it didn't seem to affect it.
Thanks for any help!
