I rode 4000 miles from New Mexico to Costa Rica. Engine started running rough and loosing power. Found a Suzuki dealer in San Isidro and we discovered the air box full of fuel. We cleaned the air filter and replaced the fuel filter. The valves and timing checked out fine. The plugs (#10) were yellow so we replaced those with new #8's. (That is what the mechanic said works best here). I then rode it another 60 miles and it was fine but when I went to start it a couple days later the engine would not turn over more than a half a cycle or so. I once again found the air box full of gas. It seems to me like there is a valve problem to cause the fuel to back up but timing and valves both checked good and it ran fine after my visit to the mechanic. Any ideas? Do I need to replace the carb jets for sea level? I rode along the coast all through Mexico, Guatemala, El Salvador, Honduras and Nicaragua without issue. I am here for a couple weeks most likely and there is a Yamaha dealer nearby but I have time and if I can save money and fix it myself that would be nice.

Update: Tried starting it again, and it seemed electrical, starter cut out. Light comes on fine and it is a new battery. I fiddled with the wiring for the starter a bit without really doing anything and it then turned over fine but required lots of gas to fire up cold even with the choke on and it took a couple tries to start. Low idle even with choke on required gas to keep it from stalling. I only ran it a minute or two. Any ideas?