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my daughter got a S'Cool bike that's a 3 speed internal hub gear system. It works fine in the first two speeds but when it goes to third gear it makes a bit of noise - like a small "whizzing" sound that often comes a few seconds when changing gears before the cassette switches over. Sorry, I'm not very technical yet on my bike knowledge.

After about a minute or two of riding in third gear the chain will pop off. She's 5 years old, very average weight so there should be nothing about too much strain on the bike. I've replicated the problem by holding the bike in the air and manually activating the pedals for about 30 seconds and then chain will pop off with almost no load.

This is the model she has (though she picked a real "pride of the irish, blazing orange color) https://www.scool.de/.cms/503-1-374

https://www.scool.de/obj/Produkte/2018/Bilder_klein/5014_3.jpg

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    How is the chain tension? If you press down the middle of the free hanging chain with a finger, it should give about 1 cm. If that's more (looser chain), you have to undo the wheel nuts, pull the wheel back a bit and redo the wheel nuts. Maybe there is a mechanism for chain tensioning, I can't see it well enough on the picture. Although this would not be directly related to the 3rd gear... – StefanS Jun 26 '18 at 7:31
  • The other possibility is the shifter cable isn't in the right place - Often the indicator window should show a dot when in the correct position. (fudgy not-answer cos I don't own one of these.) – Criggie Jun 26 '18 at 11:15
  • But would that cause a dropped chain? I did re-calibrate it and tightened the chain a bit. – motleydev Jun 26 '18 at 13:42
  • how old is the chain, and the cog? does it never slip at all in first gear even with high pressure? – don bright Jul 14 '18 at 1:18
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Put the hub in each of it's gear selections ( esp the one where the chain falls off ). Attempt to twist and push the cog. If there is any play in either regard, that is probably your issue. Could be adjustment of the shifter, but....

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