I’ve recently bought my Dad a 2004 Honda TRX450FM, the quad is a little rough but everything worked fine when it was delivered, came to ride it the other day and first gear will not engage. You can select reverse fine and you can select second gear and pull off ok in that gear and the quad goes through the rest of the gears fine. Does anyone know what this could be?

Any help would be greatly appreciated.

I’ve got some experience on bikes but this is the first quad I’ve had anything to do with.