2001 Scrambler 500 4x4

Well now I know why forward did not work. Small bits of plastic (no idea where they came from) where in the area under the gear indicator switch. They got packed into the pocket that the shift fork slides into when you select the forward gear. The plastic chips keep the shift fork from going in all the way which cause the engagement dog to not fully seat against the forward gear. The cogs on the face of the forward gear got worn down so far that forward would no longer engage. I bought the machine like this so I'm not sure exactly what happened. He said it started popping out of gear and eventually forward was gone. So I need a new forward gear. My question is how much slop should the engagement dog have on the reverse shaft? The engagement dog slides on the reverse shaft. I can wiggle the engagement dog a little. I'm guessing there is supposed to be a little slop since the dog is intended to slide freely up and down the shaft.