My crank arm fell off today while riding.

That's because you have lije no spindle on the crank arm...

This^^^^
Split the spindle evenly, and cover no more than a couple millimeters of spline with spacers.

Ok so i need spacers. My bb wasn't like how it look in the picture i try to fix it so i had to take off my bb.

You probably have too much of the spindle inserted into the other crank arm. Remove the other crank arm and tap the spindle back through the bottom bracket until there is an even amount of spindle showing on each side. Put your spacers on as needed and put the crank arms back on. Tighten your spindle bolts evenly so that you don't pull the spindle through too far to one side again.

dues there should be atleast an inch or so of splines showing.. you have like .0002 lol

DeviantBMX123 wrote:

dues there should be atleast an inch or so of splines showing.. you have like .0002 lol

DeviantBMX123 wrote:

dues there should be atleast an inch or so of splines showing.. you have like .0002 lol

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Dude i don't know what you talking about. I'm not new to bmx but new on building and knowing what to do if something breaks and trying to fix it. I know the bb is not in it right place because when my crank arm fell off it was like that but i can put it were it suppose to be. Then after that i don't know what to do what direction the cranks go the left hand crank. Does it goes in the direction you are pedaling.

It goes the opposite direction off your right one lol.

*facepalm

Take it to your local bike shop. Have them take a look at it and make sure nothing is damaged and then install it properly.

I get wanting to work on things yourself, but you can't just guess about this stuff and then ride a bike that's not safe. Imagine how this could have turned out if it came off at a worse time?

transition_chris wrote:

Take it to your local bike shop. Have them take a look at it and make sure nothing is damaged and then install it properly.

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transition_chris wrote:

Take it to your local bike shop. Have them take a look at it and make sure nothing is damaged and then install it properly.

I get wanting to work on things yourself, but you can't just guess about this stuff and then ride a bike that's not safe. Imagine how this could have turned out if it came off at a worse time?

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My crank arm fell once when i landed a flat 360 lol

Could draw you a diagram, but I think you'd be better off to see it done in person.
Chris is 100% correct. You're gonna get hurt because you don't really have the first clue what you're doing, and you could get hurt.
Take his advice, go to a shop. Watch what they do, ask some questions. Then maybe you can do it on your own.

Thanks Chris i was thinking of the same thing about going to my local shop yea i did get hurt i sprain my ankle i had jump off my bike. I know how to build a bike but i need someone to be there with me to help. I'm going to take to my bike shop.

Sometimes they wiggle loose if the pinch bolt aren't tightened evenly

kidbmx0000 wrote:

Thanks Chris i was thinking of the same thing about going to my local shop yea i did get hurt i sprain my ankle i had jump off ...more

kidbmx0000 wrote:

Thanks Chris i was thinking of the same thing about going to my local shop yea i did get hurt i sprain my ankle i had jump off my bike. I know how to build a bike but i need someone to be there with me to help. I'm going to take to my bike shop.

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Ya, I'd have them check over the bike while they are at it to let you know if anything else is up. Remember that sometimes you can put stuff together on your own, but a BMX needs to be put together very well, with everything tight, and solid if it's going to handle up to the abuse that we put them through.

Shitty about the ankle but it will heal up fast! Feel better man.