Engine warm up

I moved the clip back to the middle and changed the jet to a #70 and it got worse :(
As previously mentioned, Did you also replace the spark plug to the NGK plug and make sure that the gap is set to .025 thousandths???.

Z plugs are total Chinese crap plugs...Use an NGK-BR6HS spark plug for these things...That is about the best running plug for these motors...I wouldn't even run a Champion in a lawn mower...lol.
You can also set the needle valve to the next notch down to make it a little richer after you replace that spark plug...If all else fails after this, I would be looking at that MZ-65 knockoff pipe your using...Unless your really, really, good at tuning a pipe onto one of these bikes, you might want to consider going back to a stock pipe or pop open the wallet to buy a really premium pipe to get things running better.

Some of the guys here in the forums have done so quite successfully but they are the exception, not the rule...Maybe they will chime in about this pipe your using and how it effects the running of your motor.
Champion plugs are still made in the USA, not China like NGK.
I don't know about your NGKs but mine say Japan on them...lol.

Champion plugs were crap in the late 70s and still are...Just like Fram auto parts, filters, etc. are also total crap out of their main headquarters in Rhode Island...lol.