Hi Deermagnet. Welcome - sorry so late to chime in but been super busy here. Glad to see a fellow HOnda guy with a CL70! Awesome awesome bikes. Sounds like your on the right track... bike tuned up with the timing done correctly finally. These bikes are bulletproof.
I'm sure you read about my wiring tips with my CL70:
http://www.fourwheelforum.com/forum/showthread.php?t=228
I used to ride mine all over the local mountains and fire roads when I was young. I took the center stand off for more ground clearance (thought I put it somewhere safe but it's now gone :-(. I would flat track the bike a little around turns and jump it off anything I saw. These things are tough! I can even do wheelies on it still but I need to get some new tires and put new fork seals in the ol'boy. I got the seals but just need to force myself to take the time to do it sometime.
So what's wrong with your exhaust? It looks fine in the pictures. They all had upswept pipes as far as I know. Yours is original isn't it?