Chain falls off Bafang M620

jjavaman

New member
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Joined
Jul 7, 2023
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6
Location
Surrey BC
Hi group new guy here.
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I’m having trouble with the chain coming off the front chain ring. The bike worked great the 1st few times I took it on the trails but last Sunday the chain started falling off the chainring, I looked down and it was like a derailer pushed it onto the non existent granny gear. If I was pedaling there was no problem, when I stopped pedaling off it would come. I noticed when I stop pedaling the chain ring continues to spin, is that normal? I’m thinking since there’s no strain on the drive chain and it’s still spinning, it just comes off? Is there a clutch that disconnects the front sprocket when you stop pedaling/ using the throttle?
 
If your bike has a bad chainline and / or a loose chain, the things you described are possible. There are other things that can cause it as well. You should try to note which gear your bike is in when it happens. Here's my experience below.

The chainline on my bike isn't the greatest because my bottom bracket is wide and it has thick chain stays which pushed the motor out (3 spacers worth) and as a result the front chainring is also further out. When in 1st or 2nd my chain is louder sounding and my chain is more likely to come off than it is in 3rd thru 9th gear. It rarely comes off in gears other than 1st or 2nd. My chainline is straightest in 4th or 5th gear.
 
I took off the ring protector and put this on and it seems to have solved the problem! Thanks for your replies.
 

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