Found that out on our 4-210. When we bought it we knew it wouldn't move, was hoping for cheap and simple like a broken clutch. Turns out 75% of the over/under was in bottom of the housing. Completely rebuilt it, got it back together and ran it for like 75 hours then it just stops again, I was sick to say the least.

Got it apart and it turns out the bolts came out in the rear coupler, they were 3/8&quot;, higher serial numbers used 1/2&quot;. Bought new bolts that were slightly longer then lock tited them and placed locking jam nuts on em. New bolts in the over/under coupler were lock tited as well. No problems since.