Chain not sliding inside the gauge but riding on the top of nose sprocket teeth.

[Coralillo Lo Pro]

Wow that’s strange, they look like their quality control has gone to hell.

 

[J D]

Yeah, thats not right. Be interesting to put a caliper or micrometer on it & compare the thicknes of the drive rim to another 050 one... or measure the gap with feeler gauges & compare. If there's enough play the drive links can bind between the nose & the spur they're supposed to ride around on. Usually this only happens whe the nose sprockets are very worn or the nose has splayed apart

 

[NAKATA]

I broke another one today, that makes three 3/8 LP nose sprockets in two and a half weeks.

I started mounting them with bolts and nuts as riveting takes too much time knowingly they will brake anytime soon.

I follow a youtuber called "Belko Woods" and he has the same problem:

So its not just me struggling with those noses, maybe they are really not so great quality.

 

[Coralillo Lo Pro]

Strange. I wonder if I'll run into that with my 48" bar. Belko Woods seems to be using a 42 or 48" bar, so I wonder if it's something that happens mostly with those size bars, since my well used 36" GB lo pro has never had a problem with the nose sprocket, nor my 20" bar. Maybe the nose sprockets are just too weak for lo pro 42-48" bars and the forces involved in running longer chain loops. The other thing is they're a very small nosed tip on those bars, meaning a rapid direction change which is harder on the sprocket. I'd guess that GB just uses the same nose sprocket on all their lo pro bars and never gave thought to it not being strong enough for the longest bars. I've got a bit of play in all my nose sprockets on new bars I haven't used yet, maybe not quite as much as yours, but not much different. Not sure that's the problem. I suspect it's a problem unique to the 42 and 48" bars. It's like they made the nose sprocket to be sacrificial (by accident not by design) so on those size bars it snaps before the chain ever breaks. Never would have thought the nose sprocket repeatedly failing would be the problem with running big lo pro bars, I thought snapping chains would be the problem. They should just make a sprocketless roller nose for them.