||This is the Malossi 70cc Big Bore Kit
||You will need
to start by removing the farings. You may not want to remove all the
farings I did, but I hate clutter, and I want everything off to make it
easier. Start by removing the side covers from each side (1). Then pull
off the rubber mats that you put your feet on from both sides (2). Then
remove the front kick panel (3). Then remove the bottom faring (4). And
Finally remove the top faring where your feet rest (5) - you will need to
remove the battery to do this. Check the next picture for that step.
battery and remove it. There is a connector that attaches to the fuses
underneath the faring. Disconnect it to remove the fuse block.
||This is what
the fuse block looks like after it has been disconnected.
||OK, after you
have pulled the wires through and removed your last faring, it is now time
to start disconnecting ALL WIRE CONNECTORS, HOSES, AND CABLES from the
engine. This is what you should have now.
draining your coolant. There is a small plug just above your intake hose.
Simply remove it and the coolant will flow out. Be careful, it really
shoots out of there. It won't just drip into a bucket at first, you have
to hold the bucket in front of the hole to catch it!
your oil line for your 2-cycle oil. Also there is a breather to help your
coolant drain. Remove this screw to help your coolant drain out of the
||Ok, you will
also need to remove your air box to get to the bolt holding your rear
shock on. Also remove the connector from your throttle body at this time.
(That is the connector that is located on the intake right behind the air
||Now remove the
connectors from your fuel injector and your temperature sensor. The two
connectors are exactly the same, so mark them as to which goes to what.
You have to remove the small spring clip to get these off, just like the
connector on your throttle body. After you have them off, replace the
spring clips so you don't loose them. You can snap the plugs on with the
Also you are going to need to remove the torx head screw that holds your
fuel lines in.
||After the torx
head screw has been removed, remove the little steel clip under it. Now
you have to unplug your fuel lines. One is the intake from your fuel pump,
and one is the return line. No gas will come out of your intake line. But
gas will POUR out of the return line. I used a small piece of rubber hose,
and plugged one end with a bolt. As soon as I pulled the return line off,
I pushed the hose onto the connector. You may also just want to drain the
gas into a gas can, the choice is yours.
your coolant lines. There is a hose clamp on the hose attached to the
cylinder, but you have to break the clamps off the other hoses. You are
going to need some new hose clamps to replace these.
your air injector connector. It is hidden behind the coolant line on your
rear shock from the transmission housing, and unbolt your rear brake
caliper and remove it from the rear wheel.
spark plug wire. And if you are ABSOLUTELY SURE there is nothing else
connected to your engine, then remove the main chassis bolt from the
frame. This may require two people to lift the frame off the engine. I was
able to do it by myself, but it wasn't easy.
After the main
bolt has been removed, simply lift the entire top frame off the engine and
set it aside.
torx head bolt that holds your air injection hose on the cylinder. Then
pull the air hose out.
water line going into the cylinder, this will require breaking the clamp
off again. Also disconnect your exhaust from the cylinder.
should be completely disconnected from the cylinder and head. Remove the
four nuts that hold the head and cylinder on.
||Slide the head
and the cylinder off the four bolt posts exposing the piston. Remove any
gasket that may be stuck to the motor.
||Now, use a
small screwdriver or a pair of needle nose pliers and remove the ring clip
from one side of the piston. Push the connecting pin through from the
other side to remove the piston.
||This is all
the stock stuff you should now have removed and ready to replace it with
your new big bore kit.
||Here is a
comparison of the two cylinders. YES SIZE DOES MATTER!!! And as I always
say, "There is no replacement for displacement!" YEAH BABY!!!
||OK, now we
need to remove everything that is attached to your old cylinder head and
attach it to the new. There is an assortment of o-rings and gaskets.
Replace all that apply, put some 2-cycle oil on the o-rings before
assembling, it will help them go together easier. If you see an o-ring,
find one the same size and replace it.
Start by removing the two bolts that attach your fuel injector to the head
and remove the fuel injector.
||Next you need
to pound your air injector out of the head... Yes I said pound it out. It
is pressed in the head. Flip the head over and use a small piece of
plastic to pound the injector out from the combustion side.
your coolant intake manifold (with thermostat), and remove the temperature
||Cut off the
aluminum washer on the temperature sensor and replace it with the new one
provided in the kit. Attach everything to the new head. DO NOT TIGHTEN THE
TEMPERATURE SENSOR YET. There is not a lot of room with the new cylinder.
You have to wait until everything is back together and tighten it so you
can plug your connector on. If you tighten it now, you may not be able to
get your connector back on, and you can't loosen it after the washer is
squished or it will leak!
Don't forget to lubricate the o-rings with some 2-cycle oil before
assembling. Push the air injector in first. Seat it as best as you can.
Then put the fuel injector on top of it and tighten the two bolts down.
This will seat the air injector the rest of the way.
||Now you have
the head ready, you have to get the piston ready to go on. Insert one of
the ring clips into one side of the piston. Then put the rings on the
piston. Start by sliding one ring over the top and into the first grove on
the piston. Then work the ring down to the second groove. Now put the
second piston over the top and into the first groove. Piston rings are
hard and fragile. DO NOT stretch them too much or they will snap in
half!!! You will notice little pins sticking up inside the grooves on the
piston. These pins are to be located where the rings are split after you
put them on.
||Now the piston
is ready to install. Put the piston onto the connecting rod with the arrow
pointing to the exhaust port. Push the connecting pin through the bearing
cage and up against the ring clip you installed on the other side earlier.
Install the other ring clip on the side you just pushed the pin into.
||Now you need
to put the cylinder on. Start by using a little 2-cycle oil and lubricate
the walls of your cylinder. Also, there are bolt studs that came with your
kit, these are for your exhaust. Use your old cylinder to determine which
length you need, and screw the short end of the post into the cylinder by
your exhaust port. I only require one in mine, but there were two in the
kit. Put the gasket provided with your kit onto the four bolt posts and
slide it down to the motor. Push the cylinder onto the four bolt posts and
push it down just until the top of the piston starts to enter the
cylinder. Line your ring up with the little pin in the groove on the
piston and squeeze the first ring together and push the head down to the
second ring. Then do the same for the second ring and push the cylinder
all the way down to the motor.
the o-rings provided with the kit into the head.
||Put the head
on and tighten the four nuts up pretty snug... I don't know what the
torque setting is for them, but I just crank down on them pretty good.
Re-attach your exhaust, air injection hose and your water line (This will
require a new hose clamp).
After that, you are ready to re-assemble your scooter. Start by putting
the main chassis bolt through and re-attaching the frame to the motor.
Then hook up your brake line and other hoses, cables and connectors.
Remember to check your temperature sensor to see if you can snap your
connector on... Tighten the temperature sensor down until it is tight and
you are able to clip on your connector.
You will also have to bleed your rear brake line. Take the top faring off
around your handle bars and fill the brake fluid reservoir up and bleed
Now that the
cylinder is installed, you will now need to install the computer that came
with your kit. Start by disconnecting the connector in the bottom of the
computer. Then Remove the three bolts that hold the computer to the frame.
||Now push out
the metal centers from the rubber grommets and remove them from your old
computer and install them on the new one.
||Bolt the new
computer to the frame and plug it in.
just need to put everything back together. Start by putting the faring
that holds the battery in first. Re-install your battery and give the
motor a start. No sense in putting everything back together only to find
out something is wrong!
I have been told that sometimes you need to have a dealer clear a fault
for your scooter to run properly. If your scooter is running at high RPM's
and it is running with a real bad cough, this will have to be done. I did
not have this problem. My scooter has run fine since it was installed. I
do notice a miss here and there when I am running at low speeds, but once
I get up around 25MPH, that goes away. I have heard that this is normal.
Also the scooter tends to idol a little higher than before. I have heard
that this too is also normal.
If you do take your scooter to a dealer to have faults cleared, DO NOT LET
THEM RE-MAP YOUR COMPUTER!!!!!! Part of the reason that the big bore kit
is so expensive is because of that computer. It is programmed to run the
injectors harder for a 70cc kit. The gameboys are not capable of doing
this. If they re-map your computer, you will loose the 70cc programming
and you will be SCREWED!!!
After you change your bore to 70cc's, chances are you are going to
have to change your roller weights and/or contra spring. If you are
unclear on how the roller weights and drive train work,
click here to understand how it all
Also, I HIGHLY recommend getting the final gear drive kit with the 70cc
kit. I installed the 70cc kit on my Mojito, and the scooter had great
acceleration, but little increase in top end. Also the scooter revved up
to its highest rpm's very quickly. After the gear installation I had
better top end, and the motor isn't spinning up nearly as fast. So in my
opinion, the gear kit is a MUST HAVE with a 70cc kit.