My 1980 CB650 Custom is back with a vengeance. Something was always a little off with the bike (hard starting, burning oil, running a bit rough, etc), but it’s always been fun to ride. This spring I did a compression test and found out that #1 cylinder only had 60 psi, so I planned a top end rebuild.
Dad and I tore the bike apart within a few hours, and inspected parts as we went. We didn’t really find anything obvious, but something had to be the reason for low compression on 1...
I didn’t take many pictures last week, but we honed the cylinders, replaced the rings, lapped the valves, replaced all the top end gaskets, cleaned threads and got assembling...
Changed the oil, got the exhaust on, triple checked everything (including cranking it over until the oil pressure light went off), and it fired up! It didn’t really run good at all for 5 min, but as the rings and valves started to seat, it got better... then it smoothed right out. The carbs were way off, so we balanced them, and took it for a test ride...
The first ride wasn’t perfect. It had no low end power, so you had to goose it to take off from a stop. After that throttle response was good, but there was no happy medium. After doing some reading, and finding a replacement set of needles, I decided to try raising the needles (lowering the clip one position)... and wow what a difference. For reference, I have a K&N filter, stock 95 main jets, stock idle jets, and a 4 into one exhaust. 100 mains might be something I try down the road, but for now raising the needles has really perked this bike up!
Then I did some repainting (wheels and forks) and general freshening up... I’m super excited w the result... and now I’ll be able to ride this bike more!!
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The bike is looking nice 
I'm trying to clear floor space in my shed to work on my "80" Custom. The PO filled the motor up with metal when he helicoiled the cylinder head bolt threads, this got sucked up to the top end in an oily metallic soup and mashed up the cam bearing faces. To make matters worse, he totally screwed up some of the helicoils, so as a bodge repair he drilled out the cylinder head bolt passages and drilled into the top of the barrels (jugs US?) bolt holes, threaded the resulting larger hole then bolted the head straight to the barrels (jugs) where he had screwed up the four centre helicoils around the cam chain. The whole mess needs a replacement top engine case, cylinder head and cam shaft which I have already sourced. I have a couple of complete spare engines but I'd rather fix the broken one, that way I've still got a couple of spare engines 