Be certain that carbs are properly jetted, synched and adjusted. Removing the equalizer may affect mixture. It is possible to have hot unburned fuel from a rich idle mix to autoignite at the end of the muffler when it hits the air. Otherwise suspect stretched timing chains which result in slightly retarded cam timing, allowing unburned fuel into the exhaust.
you need new rings
clean throttle bodY?
You need to clean out your carb or need a new throttle cable
throttle positioning sensor
Because there is something wrong with it.
If you use the Honda brand, you will not go wrong.
There is no way for anyone to tell without looking at it or without you giving some sort of information about the exhaust system. You'll have to tell what it's doing wrong.
because something is wrong with the vehicle
Check the intake and exhaust manifolds around the EGR valve. There may be enough carbon buildup to prevent free flow of gasses.
I do not think you can modify the exhaust in KY . Hope Iam wrong
Throttle body issue.
Use Honda 10w40 and you will not go wrong.