3rd gear not staying engaged

[Monty]

So I have a gs500LT that has a third gear that likes to slip. Its only 3rd gear. Sometimes it will stay in gear and it will always stay in gear if I shift into 3rd and when it pops out, push down on the shift lever and hold it down.
I've gotten used to just jumping over the gear, but I wasn't sure if it was something I could easily adjust, or if its as I fear and need a tranny overhaul.

[mike-s]

I'm no expert with gearboxes but from the little i've gained over the years it may well be a damaged selector fork. The only way to check exactly what the cause is, is unfortunately to take the engine out & split it open to take a peek.

[Monty]

Okay, thats what my guessing and some googling made me think. Would it damage it more if I rode forcing it to stay in 3rd? What could cause the selector fork to do this?