That black part is the updated part i take it.......which is the same on mine, but it's orange, which means it came out of the factory that way. Looked mine over today, since i have to replace a sheer pin and noticed that that vertical bolt showing is not there, just the horizontal one. Nothing turns by hand, thinking if lost that bolt, i should be able to turn it like the auger i lost the pin from is. Got me wondering now......
That bolt going through the 2 flanges serves no purpose at all, since they are both welded onto the same tube. There is nothing to sheer. Parts manual calls it a sheer bolt....hmmm.
Mine has 150 hrs now and is ending third mowing season. No issues at all, I have the 48" deck and no other attachments. I did the 50hr service, not hard but room is small and spillage is almost unavoidable. It's stored inside and I blow it off each time with leaf blower. I does a real nice job on lawns and handles steep grade without issue. HS
I had the GR2728 (manual chute) for the GR2120 i just traded in. It works very well. Only thing about it i didn't really care for is the chain drive (auger) which needs lubricating every 4 hours. Not that it's a big issue, but it's a pain never the less. There is a access hole for a squirt gun/bottle, but it's a hit and miss trying to hit the chain. On the other hand, the cover can be removed (2 bolts) with clear view of the target. Then i had cartboard under it to catch the dripping Bar-oil (chainsaw oil is what it calls for). Had to replace 2 sheerbolts the first winter, so have a few on hand!
