Need some help finding some parts
 

Hi
My nephew got a used BMX but the crank is very much broken and need replacement. It is a GT Power Pro
I'm not familiar with BMX so don't know the age or more about the bike than that.

I'm new to the site, so cant upload pictures before post no. 10, so I have to describe it to you:
- 68mm wide
- I measured 34mm inside the threat
- To pedal arm has 7 or 8 groves to attached

On a budget, so used or cheap new is good.

Does anyone know what this type is, and where I could by a new or used one?

Thanks if you can help :)

Really hard to help without pictures. The crankset may have been changed. Even if they are original, without a picture it's hard to say. Once you reach ten posts you can post pictures. Or one of the members (someone other than me) can help out with pics. I'm computer challenged.
Where is the serial number located and what numbers does it start with. Could be letters as well. Serial number should be on the bottom bracket (the short tube the crankset assembly fits inside) or, inside the left rear dropout.

Dans Comp https://www.danscomp.com/

Hi, sounded like an 8 spline crank to me. Does it has a bolt or two right next to the splines?

After you got the spline type right, need to check the spindle size; not sure abt 8 splines, but the other type (48 spline) comes in 3 diff diameter now. Then comes the crank length. It's normally between 165 to 180mm, rider's preference. Kids might like shorter ones, and less chance to get your heel hitting the peg if you do run that. Happy hunting!