First thing I seen a similar post about a 4th gear issue and I'm having the same problem but in 5th. When I'm riding and get to 5th it's like it's jumping in and out of neutral. I've replaced all three shift forks and shift drum last summer and it has helped because it was completely dropping out of 5th. I'm guessing I need to replace the 5th gears ? any other gears to replace that could cause this ? Second issue I'm concerned about. As I said I just rebuilt the motor last summer and have about 3 hrs on the new piston (complete head rebuild too) and it has some small pitting started on the rim above the exhaust ports. What could cause that? thanks!!