How To: Swapping Out Cranks for Your Motorized Bike
Installing a new crankset will make all the difference when riding your bike with your bike engine engaged and disengaged, and you'd be surprised how easy it is to install a new crank on to your bike. Now there are two types of cranks you'll work with as a motorized bike rider: a one-piece crank and a three-piece crank. A one-piece crank is typically found on a beach cruiser or an older bike, and it's called a one-piece because the crank arms, shaft, and sprocket are all in one piece. A three-piece crank, on the other hand, has two crank arms (one with the sprocket attached) and a crankshaft- those three pieces come together to make the crank for the bike. (How do you tell if you have a one or a three-piece crank? Easy! Take a look at your crank arms. If you have to tighten one on to each side of your crankshaft you have a three-piece crank. Otherwise, if you can't take the crank arms off you're working with a one-piece crank.) Here's what you'll need to get started: One Piece Crank Tools
  • A crescent (adjustable) wrench
  • A crank lockring spanner
  • A new bottom bracket with bearings
  • A new crankset- this is where it gets tricky. If you want to keep your bike's crank the way it is now, buy a similar crank set. If you want to convert your bike from a one-piece to a three, first make sure your bike can do that, then buy the appropriate crank set to fir your frame.
  • * A mallet and chisel (if you want to remove the bearing cups)
  • * A socket wrench or Alan wrench (if you plan on converting a one piece to a three piece)
Once Piece Crank Removal
  1. Start by removing the locking nut and washers from the crank, turning counterclockwise to loosen the nut.
  2. With the spanner, take off the lockring.
  3. Keeping the other end steady, turn your crank so it will start to unfasten itself from the bearings and lock nut on the opposite side.
  4. Once loose, remove the crank from the crank port at the bottom of your bike.
One Piece Crank Installation If you're installing a new one-piece crank on your bike, start with a hammer to knock out the bearing cups in your bike. Starting from the outside working in, place the chisel on the edge of the cup and tap it out.
  1. Take the lockring spanner and remove the ring and washer holding the sprocket on to the crank arm.
  2. Put your sprocket on to the new one piece crank, assuring the ports line up on the sprocket and crank.
  3. Install the replacement washer and, with your lockring spanner, tighten the sprocket lockring on the crank tight.
  4. Take your new bearing cups and press them back in to place within the bike frame. You may need a clamp to do this, but you can use a hammer and a block of wood to assure a tight fit in the frame. IF YOU USE WOOD AND A HAMMER, be sure to use a medium amount of force. You do not want to damage your crank set or frame.
  5. Once the bearing cups are in, lube them liberally, and lube your new bearings as well with lots of grease.
  6. Slip one bearing (with the balls facing in toward your bike) on to your crank above the sprocket lock ring and slip the crank inside the frame.
  7. Lube your other bearing (with balls facing in toward your bike) and slip them over the crank into the bearing cup.
  8. Slip the other lockring on to that same crank and fasten it down until the crankset is completely within the frame.
  9. Assuring the crank is steady (it doesn't wiggle or move in any way), take your last washer and slip it over the lockring. Do the same with your last nut and, with the crescent wrench, tighten the nut snug on to the crank set.
One Piece Crank to 3 Piece If you're looking to put a three-piece crank on to your bike (say, for a wide crankset and a 4-stroke) you're going to need a three-piece crank set.
  1. Knock the bearing cups out of your frame and replace them with the cups that came with the crankset.
  2. Liberally lube the bearings and install them in the bearing cups (with the balls facing toward the inside of the bike).
  3. Install one of the lock nut on to your crank shaft and slip that shaft into the crank port.
  4. On the opposite side of the crank fasten your other lock nut, and secure both with your crescent wrench.
  5. Once both lock nuts are installed, press your crank arms on to your crankshaft and tighten them down snug. Some cranks require a socket wrench to install the cranks, others use an Alan wrench. Check to see which wrench your crankset requires.
Once you're finished all you have to do is install some pedals and you're ready to ride!

6 comments

Larry

Swapped mine out no biggie.

BikeBerry

No problem! We have a visual guide for it in our 4-stroke installation video. Just click here to view how to install the bottom bracket

BikeBerry

Hey there, Kevin! Take off the drive sprocket case cover from the motor and inspect the drive sprocket. If your chain pulls to the left your drive sprocket may not be pressed in securely. If that’s not the case, inspect the alignment of the chain, because your drive sprocket is secured but your chain pulls to the side, you might need more gaskets on your rear wheel sprocket to align the chain properly.

Tool Sets UK

Every couple of years, especially before a trip, I replace the glue for the tyre repair kit. This way I won’t have a hardened dried up tube of glue if needed. A lot of outback road signs advocate carrying two jacks (if a tyre goes flat and you fit a jack, you might not get it high enough to put on a new tyre. Not all road surfaces are suitable to dig a hole where the tyre rests with the long handled spade you are carrying.

Kevin Grimm

M planing to install my 2 stroke in my Schwinn Sting Ray . I ha a issue with counter sprocket as it moves , runs out to the left , seizes motor . Wutz up wit that ? Help ????

Mich

The replacing process seems to me very easy. I’m delighted to learn this process, however could you provide me any video of doing this work in similar fashion. It would have been better for me. Thanks.

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