How To: Installation Guide – 79cc 4-Stroke Bicycle Engine Kit

How To: Installation Guide – 79cc 4-Stroke Bicycle Engine Kit


Hey guys it’s Aaron from Bikeberry and
today we’re building a 79 CC four-stroke engine. This is currently our largest
four-stroke engine and features a pull start and center mounting design.
It’s spec’d at having three horsepower, a max of 3600 RPM, 3.5 foot-pounds of torque
and ready to hit up to 35 miles an hour. Well that’s only if you leave the
governor on. Take it off and you’ll find a whole new meaning of speed. If you’re
looking to buy this engine kit check the link in the description but be aware
there are some limitations on the bike requirements. On that note I’m gonna send
it over to Alan to cover those bike frames. Your bike needs to be a standard
male beach cruiser, road ,or hardtail mountain bike. The tubes should be 25 to
28 millimeter in diameter with an open V style frame. The frame should also have a
9 to 11 inch of clearance between the bottom bracket and top bar. The kits will
fit most 26 inch by a 1.75 inch wheel with a standard 12 or 14 gauge 36 count
spoke. If you’re in these right specifications then you’re good to go. Before we look at the motor let’s get our bike prepped for installation,
starting with the wide crack assembly. This is an optional purchase that allows
the crank to safely clear the engine, but we recommend it, to still have full use
of your pedals. Remove the left pedal and undo the lock nut and the cone. We’d
recommend using a pin face spanner to remove the cone but a flat head
screwdriver will also work. Keep in mind that the left side of the crank assembly
is always reverse threaded. Once everything is undone remove the crank
and bearings. We need to remove the cones and replace them with the new bottom
bracket. Use a metal rod and mallet to pop them out. Assemble one side of the
bottom bracket and tap it in with a soft mallet be sure to line up the bolt holes
before tapping them in place. Slide in the axle rod and the bearings,
then tighten it all up with the cone. Slide the chain ring on and use the lock
pin to hold it in place. Mount the crank arms, being sure to use
the correct side. Tighten everything down place the dust cover on and finish it
off with new petals. We got our wide cranks done, let’s take a look at the rear
wheel and put a brand new sprocket assembly on. I’mma send you over to
Johnny see how that’s done. Installing the rear sprocket is pretty
straightforward, but take care to ensure that the structure is centered and
aligned on the rear hub. If your rear wheel has a coaster brake, unbolt the
brake arm from the frame and loosen the nuts on each side of the axle to remove
the wheel. A good tip is to flip the bike upside down on the carpet to keep from
scratching the bike. Here we have it on a bike stand for a better view. Remove the
coaster brake arm. Sometimes the coaster breaks arm’s nut is too tight. If it is,
you should use leverage to remove it easier. Now fit the drive sprocket over the left
side axle and make sure it fits properly. If it does not, you may need to grind or
file the inside the hole of the sprocket to get to fit onto some bikes properly.
The preferred method, although, would be to take it to machine shop and have it
machined to the proper sizing. Place one of the rubber gaskets provided over the
threaded end of the bolts, on the opposite side the sprocket. Cut between
two of the holes on the other rubber gasket. Now place it over the axle on the
inside of the spokes and align it with the bolts on the sprocket has shown,
sandwiching the sprocket, rubber gasket, and segment over the spokes. Gather the nine
bolts provided with the sprocket and thread them through. The goal when
assembling the rear sprocket is to make sure it clears the tire, without going
over and hitting the chain. This will be the most tedious part of the build but
with patience you won’t run into any drivetrain issues when you’re starting
to ride it. Then place the three metal retaining segments over the bolts. Before tightening the sprocket bolts, it’s critical to make sure that the sprocket is centered
in the wheel. This is usually very easy to do because the center hole should
line up with the center hub. Okay, so when it comes to the coaster brake arm, after you
put on the drive sprocket, sometimes it won’t fit and it’ll hit against the
bolts. What you’re gonna want to do is you’re gonna want to bend the coaster
brake arm, and what I like to do is I like to put it in a vise, heat it up and
then just go ahead and push this back. I like to keep the vise about right here
at this line and just heat it up and it just bends right into place. Don’t over
bend it, and when you put it on it should clear the bolts like ours. Let me
just set it on. It’ll clear right over the bolts, no problem. If you’re really looking to push your
engine’s performance, you may want to consider purchasing our BBR tuning
sprocket adapter. Rather than putting all the force on the spokes, it evenly
distributes that pressure onto the hub. Now that we got some of the bike prep
out of the way, let’s take a look at the motor. It comes pre-installed with an air
filter muffler and a gas tank, we’re gonna do some modification to this
engine, removing these components. Making it fit into the bike a little better, and
making a run a lot smoother. The gas tank can be easily removed by undoing
three bolts and disconnecting the hose. Undo the two nuts securing the muffler
and check that the gasket is still in good condition. The air filter has to be completely
disassembled before it can be removed. Undo the two thumb screws
then take off the face plate. Pull off the foam filter and the screen then undo the remaining nuts.
Finish it off by checking the gasket for damage and admire this
beautiful engine. We got the engine down to its base parts, now we have to do two things.
First of all, put on a new air filter Secondly, we gotta take off the base
plate and get it ready for mounting. Slip on the adapter and securely
tighten down the nuts. The air filter will easily fit onto the adapter.
Just tighten the clamp on and it’s done The base plate is easily taken off by
undoing these four bolts. Mounting your engine will take a little trial and
error to find the perfect position. Adjust the sliding brackets on the
mounting plate so that the plate sits leveled and as low as possible, still
leaving enough space for the chain. Place the motor on the mounting plate for a
dry fit, then bolt everything down when it’s properly seated. We had just the right amount of clearance
to make our engine fit, but if you’re having more
trouble than we are, I’d recommend using our CNC’d shorthead. It’ll provide that
extra amount of clearance that you may need. During our dry install we found out
that our mounting plates were blocking our bolts, so we’re gonna go ahead and
mount this onto our engine. before dropping it onto our bike.
Line up the bolts with the slots on mounting plate and bolt them together. After that,
drop in the engine and tighten down the brackets for the mounting plate. Let’s take a look at the transmission
and the clutch. The transmission is modular. With these different size spacers you’re able to adjust the sprockets to
different positions. The clutch is a centrifuge design. Allowing the chain to be positioned on
either the inside or the outside. Installing the heavy duty transmission
is a quick and easy process of lining up the bolt holes with the slots and
bolting them together. Be sure to use the smaller bolts on the recessed slot. Remove the key stock from the keyway and
use the appropriate spacer as needed. Line up the clutch with the keyway and
slip the clutch onto the drive shaft. Tighten everything down with the provided
washer and retaining bolt. When putting on the chains, be sure to measure out the
proper length. If the chains are too long, use a chain
breaker tool to get the proper size. After the chain is cut to the proper
size use a master link to put it all back together. Once the primary drive
chain is on the transmission finish it up with the chain guard. Removing this
bolt will allow the shield to easily come off. Use the same bolt to secure the
guard and use a spacer and the extended bolt to secure the other side. If you haven’t already done so, clear the
way from the secondary drive chain. Use the same method as before to
make any adjustments to the chain. Attach the chain tensioner to the chainstay,
making sure the chain is properly in line before fully tightening it down. To install the muffler, you first need to
install an adapter. Be sure to place the gasket on before
installing the adapter. Align the second gasket and the muffler
to the adapter, then bolt them on. Our top tube is a little wide for our gas tank,
so we’ll send you over to Allen to see how we installed it. If you have a larger
diameter top tube, like this bike has, you will need the wide gas tank mount. To
install the wide gas tank mount, it requires a little bit more elbow grease
but it is definitely worth it. Take the wide gas tank mount and bend
them straight. Then bend them by where the holes are.
Do it for both brackets. Then install the gas tank. Once the gas
tank is installed, install the fuel valve, and fuel line. Install a fuel filter between the gas tank and the engine. Secure all ends with hose clamps or zip
ties. Slide on the throttle and mark the position for the guide pin. Measure the guide pin to find the proper drill size for the hole we’re going to be drilling. Start slow when drilling if a spot drill is
not available, as the drill will want to walk. Once a proper dimple is made you can
speed up the drilling process Connect the throttle cable to the
throttle grip. Push the cable through the throttle eyelet
and lay it inside the guides. Use the two bolts to complete the
throttle grip assembly. Slide the throttle cable through the guide
and connect it to the throttle lever. If your cable does not reach the lever,
find a cable with a shorter housing, or you can modify your existing cable
if it is long enough Due to the metal housing, a tool that can
cut through all of this is needed. At this, point cut off the cables ferrule,
or if the cable is long enough, cut the housing and cable altogether. Tape the end of the cable for safety and
measure out the correct length of housing that needs to be removed.
make sure there’s about a half-inch of Make sure there’s about a half inch of
cable past the bracket. Pull the cable into the sleeve, so that
it’s past the cut mark. With your cutting tool, cut the
excess housing. Crimp on a new housing ferrule, then
slide the cable through the throttle lever. Cap the cable with a ferrule or use some
solder to keep the cable from fraying. Finish the cable by tightening its lock
screw and adjust the cable tension. We’re pretty much done with our bike build, but
there’s still one thing left we have to consider. Whether we want our kill switch
coming from our engine, or if we want to come from our handlebars. If you’re happy with the pre-installed kill
switch you’re all done, but if you want another option, the throttle
comes ready with a kill switch. Disconnect the preinstalled kill switch,
and using the bullet connectors, connect the similar wires together. Connect black to black and color to color. Ffinish the bike by zip tying all loose cables. Fill the motor with .35 liters of four-stroke oil
and 87 octane, unleaded gas. After that you’re ready to ride. If you’re interested in learning more
about motorized bikes, check out our other videos, or
click on the link in the description. Thanks for watching and
enjoy the ride!