All of a sudden, out of the blue my 1978 CB550K lost mid-range power and started backfiring. I was able to make the couple of miles back home by finding an RPM range where it wasn't backfiring so bad.
I've put 2,200 miles on this bike so far. It is completely stock. I took the carbs off and cleaned the heck out of them and I did the 3,000 mile tuneup before I started riding it. I did the 3,000 mile tuneup again at 2,000 miles, just because. I was feeling pretty good about my new tuneup skills after this last one. It was idling nicely at around 1,200 RPM (once it gets warmed up) and it was making power really well. It felt nice throughout the power band. It sounds great, I love those 4 into 4 pipes.
Last night I took the points cover off to have a look. Both points seem to be wearing on one side of the contact more than the other, like half the circle was discolored. I polished the points with a burnishing file and blew out everything with electronic cleaner. I wiped down and re-greased the cam. Then I fired it up. Lightning all over the 2-3 points. Sparking all around the pivot and spring and such. I put the cover on and rode it around the block. Same thing, weird power, and backfiring. The hand test seemed to indicate fire in all four cylinders.
I'm GUESSING the condenser on that side is crap. I bought new points and condensers for that first tuneup. I still have the OEM condensers and I'll put those back on today as a troubleshooting test. Or I could swap 1-4 for 2-3.
What else should I be looking at?
My 550 is the one in the background in the little photo. My son's 1973 350F is the red bike in the foreground.
