Find where the reverse lock out cable attatches to a lever. Put the unit in reverse and check if the lever will rotate towards the cable housing more than the cable will pull it. Inside the case on like early 90's 400's, there is a arm that has to lift away from the shift drum. If it will not lift away the unit will not fully go into reverse by not allowing the shift drum to fully rotate and engauge the reverse gear assembly. If this cures the problem, wire the lever towards the cable housing and remember that when downshifting that you can hit reverse while going foreward if you pass neutral shifting down past first.
On the other hand, with the lever pulled all the way to the end of it's travel and the unit will not go into reverse, sorry to say but the reverse shift fork may be bent. Hopefully it never took all the teeth off the engaugement gear from not going in all the way.
There is one more thing that could be wrong, part of the shift drum star wheel has a reverse lockout detent on it. The detent may be out of place or worn. The shift detent can be accessed by removing an engine cover. If a fork is bent or gear is stripped the engine cases will have to be split to repair.
----- Gimpster -----
