I need a little help with this 316

I have a JD316 it has a Kohler engine model# K341AQS. I would like to find out the year it is and don't know if its in the ser# or where to find it, also I am a problem with it I have replaced the coil, carb, points, filters, plug, wires, and the motor just wants to spit and pop just like a motor in a car when it jumps time, so my question is can they jump time or is there some other problem that might be the culprit. Nothing I have done has changed they way it runs and now I need help.

Thanks
Larry