Engine Installation Overview

Building a motorized bike by Josh Larson

  1. Anton
    This is a basic guide showing some key points to remember when motorizing a bicycle.

    1. Mounting the Motor


    Put the motor on the frame upright and make sure that its sitting straight and that it also clears the chain wheel and or chain guard.
    mounting motorized bicycle motor.jpg

    Also to make sure to use the new style steel flat motor mounts not the old style cast aluminum ones the new style ones flex around the motor studs and make for a tighter fit. Do not over tighten motor studs.
    motorized bicycle motor mounting plate.jpg

    If down tube is to small use the frame adapter that comes in the kit but throw the weak 10mm bolt away and replace it with a bulkier stud that wont strip or snap.
    motorized bicycle frame adapter mount.jpg

    Drill a hole in the frame exactly where u want your motor to sit. You can do this by setting the motor on the frame and marking lines on each side of front motor mount where u want it to sit on the down tube. Then take the motor off and mark where the hole should be right in between the lines. Use a punchall or nail to make sure the drill bit doesn’t slip out of place. When your done the kit had bolts that replace the studs that come on the motor. And it should look like this.
    motorized bicycle engine mounted.jpg


    2. Mounting the sprocket

    Ok first thing you do is take the wheel off the bike. Take the coaster brake arm off and under that there is a little metal dust cover. Get rid of it.
    motorized bicycle coaster brake dust cover.jpg

    Now take your rubber mounts that come in the kit and cut one between the holes and put it on the inside of the spokes around the hub. Take your other rubber mount and put it on the other side. Put the sprocket over the mount and put the bolts with the heads on the sprocket. Don’t put washers or lock washers between the bolt and sprocket. Also if your using a standard sprocket that comes in the kit put it so lip under the teeth is facing out to keep the chain from rubbing the tire.
    motorized bicycle rear sprocket mounted.jpg

    Put the bolts threw the rubber mounts and threw between the little gaps where the spokes meet at the smallest part not the biggest part the bolts should fit perfectly in all the little triangles where the spokes get closest to the hub. Put your other rubber mount on the bolts and put the backing plates on followed by the washers and lock washers. Then bolt it all down making sure the sprocket is level. It should look like this when complete:
    motiorized bicycle rear sprocket mounting bolts.jpg

    Now that you have the sprocket on you need to bend the coaster break arm to fit around the bolts. Take biggest part of the coaster break arm, the part that hooks up to the hub and bend it and hit it so it’s about a 45* angle then take the smaller end and bend it so its about the same angle. It should look like this.
    motiorized bicycle coaster brake arm bending.jpg


    3. Isolating the gas tank

    Take the gas tank and put it on the frame using a piece of rubber inner-tube as a buffer between the frame and your tank. This will eliminate vibration and rattling from the tank.
    motorized bicycle tank mounting.jpg


    4. Chain

    Chain tensioners work a lot better on the longer bikes with longer chains but if you have a beach cruiser there isn’t really a need for one. To get a chain to work on a bike with out a tensioner is kind of tricky. So here it is Get the peddling chain the perfect tension by adjusting the wheel back to the chain is tight but not to tight. Then take your drive chain and hook it up to the motor and drive sprocket. Make sure both chains are not to loose. If you can’t get one chain even with the other you’re going to most likely change the peddling sprocket size or off setting the sprocket teeth. This is done by removing the little ring in front of the sprocket and changing the sprocket from either even number of teeth or odd number of teeth. If you have an even number of teeth and the chains are not lining up you need an odd number of teeth and vice a versa. Once you do that put the wheel back on and the chains should be even and the right tension on both sides.
    motorized bicycle front sprockets.jpg

    If u want to use the chain tensioner. Line it up and make sure everything is straight and tighten it up then take self threading screws and drill then threw the tensioner into the frame. This will keep it from sliding and jamming into your spokes.


    5. Clutch

    This is an easy part Take the clutch cable with the black sleeve over it take the little metal spring and put it somewhere else you do not need it. The bigger spring slides over the housing and keeps It from melting. Slide the cable threw the guide under the carb on the right side of the motor. Then take the clutch arm and make sure it’s even with the side of the motor. Take the brass cable color and slide it down the end of the cable and put it just a little bit in front of the clutch arm with the cable not strung threw it yet tighten the cable color then string it threw the frame and your done. Don’t cut the cable string it in front of the clutch arm and under the jug of the motor to keep it from sticking your leg and fraying. It should look like this:
    motorized bicycle clutch cable mounting.jpg


    6. CDI box

    The CDI comes with 2 mounts one for a fatter down tube and one for a standard down tube. The one for a fatter down tube is just a straight black piece of metal with holes on each end in your motor kit. You have to bend it yourself. The other one looks like this and usually is attached to the CDI when you open the kit.
    motorized bicycle CDI box mounting.jpg

    The CDI has 2 wires coming out of the bottom these are blue and black. They connect to the blue and black wires that are sticking out of the motor. The white wire is a kill wire which hooks up to the red kill switch in the kit.
    motorized bicycle CDI wires.jpg

    The kill switch.
    motorized bicycle kill switch mounting.jpg

    ....and there you go everything else it pretty much self explanatory. Good luck keep in mind these are pics from both of my bikes and they are dirty as hell from my mexico trip.