||One of the first and most important
modifications you should do. A 2-stroke motor's exhaust helps
determine your maximum rpm and your power band range. Changing the
exhaust from a stock to a performance exhaust will typically increase the
horsepower by 1hp. For the cost, this is a significant increase.
Also 2-stroke motors don't develop much torque at low rpm's. With
the addition of a new exhaust, your rpm's will increase, giving your motor
more torque. You will normally have to change your roller weights,
contra spring, and clutch springs to compensate for the increase in rpm's.
Which exhaust is best for your motor is hard to say. Different pipes
are tuned for different applications. If you are going to a big bore
kit, be sure to purchase a pipe that is tuned for your size motor.
Different pipes have different rpm and power band characteristics.
You can usually go to the manufacturer's website and find these
specifications. Another good way to decide which pipe is best for
you is to ask. Ask in a forum for opinions on which pipe is best
suited for your needs.
|Big Bore Kits
||Obviously one of the biggest and most sought
after performance modifications you can do to your scooter. A big
bore kit increases the size of your cylinder and in turn gives you a large
increase in horsepower. Be aware that just because you are going to
a larger cylinder doesn't mean it is better. There are several
different classifications of big bore kits. A stock 50cc scooter
usually generates around 4-5hp and runs around 7000rpm's. A mild
70cc kit will usually increase that to about 8hp and run around 8-9000rpm's. But there are high performance big bore kits that will
generate an excess of 20hp at a staggering 20,000 rpm's!!! These are
typically only for race applications and are not used for every day
riders. The engine life of these high performance kits are usually
very low. So depending what you are looking to do with your scooter,
carefully choose a cylinder that best fits your needs. Usually a
middle of the road performance kit that runs at about 9-12,000rpm's and
generates about 10hp is
usually the best choice for most people.
When you go to a big bore kit,
you will need to purchase a pipe that compliments your cylinder.
Different cylinders have different port timings. Putting the wrong
pipe on can significantly impair the performance of your new cylinder.
Try to get a pipe that is tuned for your cylinders port timing settings.
You can usually get this information from the manufacturer or by asking in
Another thing that will be needed with bigger cylinder is a bigger
carburetor. Once you increase the size of your cylinder, more air
needs to get into the motor to fill the chamber. Changing your
cylinder and using a stock carb is pretty much a waste of you increased
displacement. Again choosing the right carb for your set up is
One last thing to consider when up-grading to a larger cylinder is to
change your final drive gearing. Decreasing your gear ratio will
give you more top end. While the addition of a big bore kit gives
you more horsepower, it usually doesn't increase your top speed much.
You will get much better acceleration due to the increase in torque, but
the rpm's of the motor will still top out near stock values. When a
lower gear ratio is used, it enables you to utilize your increase in
horsepower so you can increase your top end.
||New variators are not always required. A
common misconception is that a variator will increase your top end.
This is typically not true. The performance variators are typically
the same diameter of the stock variator, so increasing your top end is
really impossible. What a performance variator does do is level out
your acceleration. The ramp plates on performance variators are
different from stock and the size of the rollers are also different.
This makes for a more smooth and constant acceleration. But if you
have good consistent acceleration with your stock variator, upgrading to a
new variator is pretty much a waste of your money. However, if you
have inconsistent accelerations, jumpy starts, dead spots, or any other
problems with your acceleration, a performance variator may be in your best
||A performance clutch doesn't help with your
top end or your acceleration. A performance clutch is only used to
help adjust and fine tune the engaging rpm's. There are a few
aspects that make a clutch a "Performance" clutch. First is the
number and size of the clutch pads. Surface area of the pads make it
grip better to the bell housing, making the clutch grab better. Also
there are clutches that have fine adjustment capabilities. Meaning
that instead of having to change springs when you want to adjust your
engaging rpm's, you simply turn a screw and tighten the spring up.
This is the type of clutch I prefer and recommend. It is much easier
to adjust than the type you change springs with, and it has a much finer
adjustment. With the type you change springs with, you only have the
settings that the different springs available give you. With the
adjustable type, you can turn the screw a whole revolution, a quarter
revolution, or what ever you want! It is very nice to finely adjust
the clutch to exactly where you want it. You also don't need to buy
several different spring sets.
|New Contra Springs
||Contra springs are only used as a tuning part.
You will only need to change the spring when you are trying to correct an
acceleration/top end problem. Read the article on the transmission
to learn more about which spring you might need or if you need one.
|New Roller Weights
||Roller weights are also used as a tuning part.
You only need to change your roller weights if you are trying to correct
an acceleration/top end problem. Read the article on the
transmission to learn more about which rollers you might need.
||Carbon reeds typically come in a set that
contains several different thicknesses. The idea is that a thinner
reed will respond faster to different pressure changes within the crank
case. Meaning that it will open when your motor makes the slightest
demand for air. The downfall of this is that at higher RPM's, the
reeds will tend to "Float" not allowing the reeds to close all the way
between strokes. Thicker reeds don't have the response of the
thinner reeds, but are more reliable at higher RPM's.
Now having said
that, most people with a typical application will not notice a difference
in the different thicknesses. Only extreme race set ups will a
performance difference be noticeable. What does this mean for you?
It means if you purchase them for your scoot, don't expect to see any
performance increase from them.
The one main reason why people use carbon reeds is for engine
preservation. Reed valves have a nasty tendency to break.
After all, they are simply really thin flaps that are bent open and
slammed shut thousands of times over and over again. The stock reeds
are made of steel. If the steel reeds break, chunks of steel are
dropped down into your crank case causing catastrophic damage to your
motors innards. Carbon reeds are much safer because if they break
and fall into your crank case, the resin that makes up the carbon reeds
simply melts and burns off. This saves your motor from serious work
if a reed fails.
||A new carburetor is usually needed when you
upgrade to a big bore kit. The size of the carburetor is determined
by the size of the orifice where the air comes in. a 17mm carburetor has a
17mm diameter opening. A 17mm vs. a 20mm carb is really only
going to differ in the diameter of this orifice... The main jet will
be a bit larger to compensate for the larger amount of air coming in.
A bigger carburetor isn't always better. You only need a carburetor
that is big enough to air to flow freely and fill the cylinder. If
you go with a carb that is too large, you will have trouble getting your
air/fuel mixture correct.
|New Final Gearing
||The purpose changing your final
drive gears is to give you more top end while at the same time decreasing
your rpm's. The peak horsepower of you engine is typically generated at
around 7000-8000 rpm's stock. Stock, if your running say 40mph at
8000rpm, from then on you are increasing your RPM's and decreasing your
horsepower while trying to go faster. The gearing just uses the full
potential of your variator, and makes it so when you are at say 8000rpm
your peak horsepower, you will now be going 50mph instead of 40mph.
However, stock 50cc cylinders really don't generate enough horsepower to
push the scooter through the air any faster than it can with the current
gearing installed. So going with different gearing on a stock
cylinder is usually a waste. However, a gear kit with the addition
of big bore kit is usually a big benefit.
||Kevlar belts are pretty much the same as the
stock belt. The only difference is that they are stronger and wear a
little better than stock. If you are going to a higher performance
scooter, it is usually advised to get the stronger belt. This belt
will do nothing for performance. It is simply stronger to help cope
with the increased torque of a modified motor. My advice is don't
worry about replacing it until you have a problem with your stock belt.
||A tuning part that helps determine at what rpm
your rear clutch engages. Remember that a 2-stroke motor doesn't
develop any torque at low rpm's. So if your clutch is engaging early
and trying to push your scooter at say 2000 RPM's, then you probably need
to go to a heavier clutch spring. Going to a heavier spring will
allow your motor to spin up to higher rpm's before the clutch engages and
pushes you along. This in turn will give you better
acceleration because you are moving while in your power band range.
||There are several different levels of
performance shocks. There are adjustable, gas shocks, internal
spring and gas shocks, the list goes on and on. Basically the only
reason for a new shock is if yours has gone bad, or you simply don't like
the ride you are getting from your stock shock. With performance
shocks, you pretty much get what you pay for. If you buy a $50
shock, expect it to be pretty much the same as your stock shock. If
you pay $300 for your shock, expect to get a really nice ride, and have
plenty of adjustments to it also.
||A torque driver is the front half of your rear
pulley of your transmission. This half of your pulley has angled
grooves cut into it to help lower your transmission's ratio when the
scooter's rear wheel comes under torque. Meaning that it is designed
to "Down shift" your scooter when you start up hills or come under a
heavier load like going into a heavy wind. The performance drivers
have a steeper angle on the pulley to help "Down shift" faster when the
rear wheel is put under heavier loads.
||A performance crank in most cases are not
required. Many will say that a stock crank will not handle a 70cc
kit. In most cases this usually isn't true. The only time you
really "Need" a performance crank is when you are running a pretty extreme
set up. What I mean is this, a stock 50cc cylinder usually runs
around 7-8000rpm's and makes about 5hp. A standard 70cc kit will
usually run around 8-10,000rpm's and make about 10hp. Your stock crank
can usually deal with this increase in rev's and the higher torque.
Now if you purchase a higher performance cylinder that is rated to run
12,000rpm's or higher and generates say 15hp or better, then yes, you should plan on purchasing a new
crank with your cylinder. The stock crank simply won't hold up to
this type of application.
Also if your stock crank ever does bite the
dust, or your bearings go, it is a good time to upgrade to a performance
crank even if you aren't running an extreme set up. A stock crank is going
to run about the same price as the performance crank, so you might as well
go with the better crank.