The old '80 CB650 was starting to smoke pretty badly at intersections and idle. Started about 5 years ago and had gotten to the point that I would just shut her down at stoplights to prevent the intersection from filling with smoke. Kind of a hassle at night as oncoming cars would usually stop and flash THEIR headlights as I was starting my bike because MY headlight shuts off when I hit the starter. That got old quickly.
I finally ordered some new Viton valve stem seals off of "feeBay" last week for $25 bux. Managed to keep the head on and do the "rope trick" to keep the valves from falling in. Had to design a few new tools to compress the springs, but with the help of my wife, I was able to safely replace all 8 seals in about 45 minutes. Took another hour or so to replace the top cover and adjust the tappets to specs.
Stripped the end bolt on top cover right side. Guess it's a common occurance and I figured out why... Tighten the very end (cam ends) bolts very last. Do the other zillion 8MMs first in several steps, ending at 7 lb/# each. THEN do the cam end ones. They are NOT long enough and they only use about 1/4 of the threads available. I swapped a longer bolt from the middle area of the top cover with the end one and it worked great.
Anywho, I can now drive across town with a hot motor and actually NOT get told that my bike is on fire at stoplights! After driving like this for the better part of 10 years, it's really nice to have a normal bike. Now I can concentrate on re-jetting (replaced the PD50s with '76 750 carbs a while ago) and other little issues.
So, if your 30+ year old bike is smoking at idle only, I suggest ordering the new viton seals and slapping them in. It's worth it.
