Small Engine Troubleshooting Problems? Ask a Mechanic Now.
It is possible that you may have some water in the fuel. This will cause a miss. Is the generator using the same fuel source as the RV?
Another possibility is that a valve has some carbon building up or the intake and exhaust valves are out of adjustment. Can you inspect those for clearance and do a leak down on the unit?
Another test you can perform is to put a spark tester inline with the spark plug wire and visually see if the spark is breaking down.
Code 14 is an "Over Frequency Fault". This could mean the RPM of the generator is running too fast so check the RPM as well.
Please let me know if you found anything else in your inspection and evaluation.