Going on main jet from 85 to 72 is a huge jump. Added to i it is the fact that most after market jets are not accurate according to the numbering. So i would suggest resetting the jet to its stock number.
However the issue of race going up and down in itself might be due to the spring and race cable. Make sure it's free to move.
Remove the carb from bike and look into it from the air filter side while the race cable is still attached to it. Fully rotates the race and s see if the slide in carb is fully lifted and then release the race to see if the slide sits flush.
The cable and spring might be getting stuck somewhere.
Regarding the timing chain issue I doubt you will need replacement.
It might need readjustment. Do from good mechanic.
Good shops are mohamdi autos and moon autos.
Sent from my GT-I9300 using Tapatalk 2