Crank falling off

[pgrbff]

The crank on one side of my son's e Haibike fell off this morning. I took everything apart, cleaned it all well and reassembled it. I didn't have an 8mm hex to put on the torque wrench, I'm not used to bikes but by car standards, 55N is not a lot. the outer 10mm was done up to the required 15N.
It fell off again. The inner bolt had come undone and it is covered in aluminium dust.
I think at some stage it must have come off and he just quickly did it up again, the teeth on the crank are a bit mangled at the ends, but it felt solid enough when I put it back together.
Any ideas? I have no idea about bikes.

 

[luna87824]

What motor...

 

[pgrbff]

What motor...

yamaha pw x2?

 

[pgrbff]

Reading some of the old threads it looks like the cranks will need to be replaced. I have never been able to get a spec list for the bike as it is a special produced for the Italian market.
What do I need to know when looking for new cranks? Just which motor they will be used with? In this case a Yamaha PW X2.

 

[Paulquattro]

Welcome to the forum

 

[Jay Bird]

Reading some of the old threads it looks like the cranks will need to be replaced. I have never been able to get a spec list for the bike as it is a special produced for the Italian market.
What do I need to know when looking for new cranks? Just which motor they will be used with? In this case a Yamaha PW X2.

I don’t know about that brand but for a shimano motor yes there are certain cranks that are “approved” for it. I’d guess yours is the same.