Crank gear/arm not going back on

T

Tom3holer

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Aug 11, 2025
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Cape Cod
Hi,
The most curious thing happened as I was replacing my crank arm for a larger size to help with ghost pedaling.
Both the gear and opposite arm came off very easily with the park tool.

When I went to replace the gear and associated pedal neither would go on very far. I was afraid I was going to strip the hex bolt.
I then decided to replace them with the original set and had the same issue.
There is a couple of pictures. Thought I best stop and ask the experts.
The bike is a K6 Euybike but the fact that the original ones will not go on any further that the new ones is a puzzle.
My thought was to coat the spindle with Never-seize. I do have an impact wrench with the correct allen socket but from what I have read and videos it should not came to that.
Has anyone seen this before?

IMG_5154.jpgIMG_5153.jpg
 
It is odd that the old ones won't go back on. With no crank arms at all and cleaning out the threads, how do the hex bolts seem? Are you using the original bolts and is one worse than the other? One more thought, how long is your allen wrench? You may need more leverage, but you don't want to go to an impact.
 
Also, another thought, maybe your square shanks are not very square. You can try removing an arm and turning it a quarter turn to the next face on the bracket. It may want to be exactly where it originated. You should put a little grease on the bracket arms, that way they won't seize up with the weather and be hard to get off the next time. Let us know how it goes.
 
I'am back; still frustrated. I Never-seized the shank and greased the allen screw and it was almost the same.
I used a new Park-tool for removal and like I said it they came off with little effort so I don't think it was a faulty removal tool.
May try to bring it to a bike shop tomorrow.
Will try rotating and see what that does.
If I knew the specs of the lower bracket/spindle I coyld get a tool and replace it tomorrow with Amazon overnight shipping
Maybe somehow the Park tool flared the end of the spindle and it is hanging up there.
If can get someone to look at it tomorrow that's what I'll do.
 
Hi again. I think I might have this figured out. Did you buy the crank arms in the other thread? Those have a diamond orientation, not a square face. They can differ enough that they will not go fully on. The tapering will be a bit off. You then may have slightly chowdered your bottom bracket.

Screenshot_20250907-183833_Chrome.jpg
Screenshot_20250907-184424_Chrome.jpg
 
If you want to go to a different front sprocket I would suggest that you find one that will fit on a set of square hole cranks like these and if you are having trouble with ghost pedaling try a slightly shorter crank length, while you are at it. This page on Amazon has the schematics there, so you can check all of your measurements for whatever sprocket you choose.
Screenshot_20250907-185846_Chrome.jpg
 
Both the original and the new ones are the diamond shape.
I will check in the morning and see if there is an orientation that goes on further than the others with the original cranks.
If so I will try it with the new crank arme and see if that works.
 
must be keyed somehow try all 4 positions. one orientation will go on farther without much effort. Rule #4: don't force anything.
 
Tom3holer said:
Both the original and the new ones are the diamond shape.
I will check in the morning and see if there is an orientation that goes on further than the others with the original cranks.
If so I will try it with the new crank arme and see if that works.
Click to expand...
OK, that is very unusual. Most ebikes have square openings on cranks. It is usually analog road bikes that are set up with the vertical diamond opening.
 
Well I think I figured it out.
In my defense I was misled by all the videos I watched and how easy it was. Most showed, using a maybe 5" Allen wrench and a bit of effort.
Thats what I tried but it was worrying me I would strip the bolt.

I Took out my torque wrench and set it to 25fp or 34nm and stopped there. I was afraid my 8mm socket felt like it would strip the head of the screw it just felt a little wonky if you know what I mean.
One issue I ran into was the new sprocket is a bit bigger, 54 teeth, but it seems the sprocket itself is set back or inward further. It was actually a blessing, not trying to get it fully on, in that the chain runs close to the battery on 1st gear and probably would been rubbing. I may try and find a different chainring.

Thank you everyone for all the help. Included is a couple of pictures

IMG_5160.jpgIMG_5158.jpg
 
Should the left crank arm in the photo from my previous post not be closer to the pickup with 34nm of torque?
The original was a bout 1/4" or less away.
Still not convinced, something is wrong I think.
I ordered two sets of crank arm bolts as I have torqued these several times.
 
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