1. Let me first start with the fact that I am
NOT a mechanic. I have been working on motorcycles and scooters for
a long time and know a little about what I am doing. I simply take
pictures for other people to use as a guideline to help them modify their
own motors. Any modifications you perform are done completely at
your own risk and liability.
2. Tampering with your motor in any way may void your warranty.
Make sure this is a sacrifice you are willing to make before you begin
working on your own vehicle.
3. Before you begin, read this ENTIRE article from start to
finish so you know exactly what is involved and what steps are required
to properly complete the procedure. Also make sure you have a nice
clean area to work in.
4. This example was performed on a 2006 Sachs MadAss 50cc
ALL bolts and socket head cap screws are in metric! Don't try to work on
your vehicle if you don't have metric tools, you will just wind up messing
up the heads.
|The stock front
sprocket (Pinion) on the MadAss is an 11T 420 and the rear sprocket is a
53T 420. If you do the gear ratio, the stock ratio is 4.8 : 1
That means for every 4.8 revolutions on the front pinion, the rear wheel
will turn 1 time.
Our New Lifan 150 came with a 16T 420 gear on it. When we first rode
the bike with the new setup, it was very obvious that the gearing was
WAY too low. The front end came up all too easy and 1st gear was
very short. 10 feet and you had to shift... Which
pretty much rendered 1st gear useless. I was actually starting out
in 2nd gear most of the time. The 16T on the front and 53T on the
rear gave us a ration of 3.3 : 1
Well we searched for a new rear sprocket all over the internet. The
OEM sprocket is 108mm center hub with 123mm bolt pattern. The only
place we could find anything that would fit was from our friends over at
OO RACING which they are having
custom made by Talon Sprockets. They featured a
sprocket kit for the MadAss which included a 15T 428 sprocket and a
43T 428 sprocket. So now we had to also upgrade to the larger 428
chain. The new 15T 43T combo dropped our ratio down to 2.86 : 1
When we installed the new set, things started to get very interesting.
Tons of low end power still available, but made 1st gear much taller and
very usable. Gears were nicely together and all around had a great
feel to the bike. However, once we had the bike broken in and we
started inching toward our top end range, we soon found that the bike
was still geared a bit too low. Not bad, but not quite right.
We found that running at about 60MPH, we were revving the bike to about
9000 RPMs or more. It also felt like the bike had a bit more to
give, but was simply out of our reach due to the gear setup.
So we went and purchased a 16T 428 for the front, bringing our ratio down
to 2.68 : 1
Now we are getting closer to optimal performance! Cruising at about 55-60 MPH, we are running at
about 7500 RPM... Considering our peak
HP is is rated to be ~ 15BHp @ 7500 RPM. Now if you want to push
the bike a bit harder, you can achieve speeds up to ~ 70 MPH at about
8500-9000 RPMs. But I wouldn't advise holding those revs for too
After riding the bike for a while and having a few discussion with our
friends at Fast Trails Performance,
they decided to get a 39T rear sprocket made. Considering that we
still seemed to have plenty of low end power, and knowing that we are
running at about 55MPH at our peak BHp RPM, we decided to aim for our
peak torque rating instead. When shifting into 4th gear, you can
throttle the motor and it pulls great. Our peak torque value is in
the 4000-4500RPM range. So we wanted to aim for 55MPH in the
4500RPM Range instead of the current 7500RPM range.
So we went with the 16T/39T combo bringing our ratio down to 2.44 : 1
All we can say is WOW! It now feels like we are in the optimal
operating range for this motor! First gear is even more useful,
still able to pull wheelies with no problem. But all the gears
seem to come together in a much smoother and more pull than ever before.
The lower gearing definitely brings out the bottom end torque of this
motor and and it is fantastic. So in our opinion, the
39T rear sprocket from Fast Trails is definitely the way to go.
you are still able to drop the ratio more by going to a 17T front, but
you are also able to increase it quite a bit by going to 15,14, or 13T
on the front. So there is still plenty of customization for people
out there who want to tweak it to there exact liking!