How do u remove a chainheel on a bmx bike?

cuz i am gunna buy a new one...i was just wondering if u just take off the crank arm and then loosen that slimish bolt and it slides off or wat?

Nooooo! Do not spary WD-40 on your crank. Loosen the small bolt that holds the chainwheel to the crankarm first, then take the crankarm off. If you don't loosen the chainwheel bolt first, it can be hard to get off after the crankarm has been removed because you can't get any leverage. After you put the new chainwheel on, be sure to put grease, not WD-40, on your spindle and inside your crankarm. This will keep everything in smooth working order and it will keep it from creaking. Once the crankarm is back on with the new chainwheel there is one more thing before tightening the chainwheel bolt. Spin your cranks backwards 2 or 3 revolutions and gently squeeze the top and bottom parts of your chain together every quarter of a turn or so. This will center your chainwheel so that you won't have hops in it, causing tight or loose spots in your chain. Now tighten that last bolt and go shred.

A good rule of thumb for any bike maintenence is to use grease anywhere metal touches metal. For instance, any part that threads in, such as, allen bolts, pedals, and axel nuts. And also use it when installing bearings. You can get good grease at a bicycle shop or use bearing grease from an auto parts store. Both work fine.

Good Luck!

spray WD40 then you remove the arm and loosen the bolts i'v changed a lot of cranks.