Mini Drag Bike
came about from wondering how fast I could make one of those
little Chinese import pocket bikes go without doing a complete
engine swap. I also wanted the project to look cool, have
better handling, and sound much better.
Here is the original bike, straight
out of the crate
I purchased a
couple of pocket bikes and decided on using the yellow one
for modifying. It came with a 50cc 4-stroke engine and was
a fun, zippy little bike to begin with. A few modifications
wouldn't hurt though.
The stock bike parked beside my Suzuki
GSX-R 600 race bike
The bike is considerably
smaller than a full sized sportbike, and it is smaller than
a YSR as well. Not made for street legal riding, these pocket
bikes are really for kids, big kids included
I don't have
any good pictures of the construction of the parts for this
bike. I do have some initial 3D renderings of the nitrous
system though. It was designed in Solid Works and the parts
were machined out for the system. Two of the different nitrous
systems are show below.
Two can nitrous system
This is the 2
canister nitrous system 3D rendering.
Five can nitrous system
Here is the 5
canister nitrous system 3D rendering. The canisters are
the type commonly used in whipped cream makers and are readily
available. The puncturing devices feature a one way valve
to keep back pressure from escaping when there is not a
full cylinder in place. A 12 volt solenoid delivers the
nitrous through a braided stainless line to the carburetor's
air filter. The system is a fogger type, and as the nitrous
flows into the carburetor, it pushes past the venturi and
picks up the extra fuel for the engine.
Nitrous is not
a flammable gas. It simply supplies more air for the fuel
to burn. By doing this, more fuel can be supplied as well.
More fuel means more power. The nitrous is stored in a compressed
liquid form in the canisters. Think of the whole system
as a liquid supercharger, or turbocharger, for the engine.
A few pictures
of the finished bike are below.
Mini Drag Bike
Here is the finished
bike. The aggressive stance makes this little bike look
good. It is a blast to drive, and handling is improved over
stock thanks to the extended wheelbase.
The swingarm is a one foot extension
placement of the rear tire was completely underneath the
rear fairing, as can be seen in the photos at the top of
the page. With the tire moved well back, it has that drag
The nitrous kit is a 4 canister model
The nitrous kit
mounted to the bike is a 4 canister model. The canisters
feed into the billet aluminum manifold block, and on to
the stainless solenoid valve. Braided stainless steel hose
connects the valve to the carburetor, and can be seen extending
from the left of the solenoid valve and up into the side
of the front fairing.
The view of the
swingarm here shows that it is basketed, meaning that it
has the additional support running side to side for extra
rigidity. Not visible are the blue lights that illuminate
the underside of the bike at night.
Low, lean, and mean
of the swingarm and nitrous kit, the engine was rebuilt
and a larger carburetor was installed. The restriction devices
were removed from the throttle assembly to allow for full
throttle movement. With the restrictors in, the throttle
could only be opened half way. The exhaust system was removed
and all restrictions were eliminated. The pipes were brought
up to a larger diameter, and the system was reinstalled.
With the modified exhaust, the system runs 1 into 2, or
1 cylinder output to 2 separate pipes and mufflers. Having
little or no restriction means more power output, and the
exhaust note is now very low, mean, and loud. It is very
loud, actually louder than my GSX-R.
So far, the top
speed of the bike has been 70 MPH with my 200 pound frame
on it. Although I had originally wanted to break the 100
MPH mark, I am happy with the outcome. 100 MPH might have
been pushing the 10 inch tires as well. Since the manufacturer
states the top speed of the bike is 30 MPH with restriction
in place, I am happy with the results. I tested the bike
with the throttle restrictors removed and reached almost
50 MPH with just a little tuning. Since the speed is most
likely estimated by the manufacturer for a 100 pound rider,
I think I did OK with the modifications.
All in all, this
is a fun bike. 70 MPH this close to the ground is a scary
experience though. Later, I may revisit this experiment
and open the engine back up to install a lock up clutch
on the CVT transmission and a smaller rear sprocket to see
how fast I can push it.
Thanks for reading,
and be sure to check out our other projects.
Russ W. Moore
Bad Brothers Racing