Trinity's 90cc Motor Build Up
your kid ride a Kasea, Predator, or an Alpha Sport? How many
times have you heard this before, "Dad, I want to go faster?"
I know I have gotten sick of hearing that from my daughter, so
I decided to do something about it.
are a handful of companies out there that specialize in the
world of kids ATVs. After numerous hours of talking with
various companies we decided to send our motor out to
Trinity Racing to have them do their magic. The Tech
Person at Trinity was very helpful in pointing us in the
correct direction for our motor project. The motor package
that they recommended, consisted of a
Trinity Stage IV Aluminum Head, mild cylinder porting,
Trinity Stage IV pipe, 20mm Keihin Carb kit, K&N Air Filter,
and new clutches. All these components are complete bolt-ons
without having to split the cases.
stock head on our Alpha Sport is of a very poor design, to
which we are trying to get maximum performance out of.
Although the head can be improved by having it cut, it still
is not as good as a Trinity’s Stage IV Aluminum Head. The
aluminum head cools better and is lighter, given the ATV
reduced heat buildup which helps keep power at a constant.
also does a wide range of
porting on these cylinders. For this project, we wanted to
keep the machine ride able so we chose a mild port work. By
doing this, we left our options open for more power as our
rider gets bigger and more experienced.
the list of installations was the pipe. For those of you that
have never seen the stock pipe on this ATV, it is basically a
straight pipe with a muffler clipped on. This setup hinders
performance and is also very heavy. The
Trinity Stage IV pipe is a 3 pipe design in which the
stock oil tank and battery box have to be removed. With the
tight confines of these quads there is just no other way to
route it to achieve maximum performance and to keep the rider
protected from getting burnt or getting the pipe damaged
during normal riding conditions.
we have the cylinder and head setup for more performance and a
quality exhaust to remove the spent charge, we need to feed
this thing. For this, Trinity opted for a
carbon fiber reed cage setup and a
20mm Keihin carb with a clamp on K&N filter. The K&N
filter is a nice replacement over the restricted stock
airbox setup. For a motor with this potential, replacing the
stock carb and reeds with this setup will not only improve
performance, but will also make it easier for fine tuning
adjustments. All jets are readily available for this carb at
any aftermarket distributor.
now have a motor combination that puts out considerably more
power. Therefore, we need to address getting this increased
power from the crank to the ground. Unlike most Sport Quads in
which it would just be a matter of changing the gearing, these
ATVs use a CVT setup. It doesn't matter how much power the
motor makes, if these ATVs are not clutched properly you are
not going to see an increase in performance. For this Trinity
changes the front Variator, uses different
weights, a wider
Kevlar belt with a
Delta Performance rear clutch.
the motor was at Trinity, they also remove the oil injection
and the starter motor, no sense in carrying around added
weight. With the motor back in our hands, we bolted it into our
Alpha Sport 90. The carb, pipe, and air-filter installed with
ease. This brings us to the one thing we did not like about
this kit, the air-filter sits right next to the front tire and
if riding in adverse conditions, every time you turn to the
left, the tire throws debris up on the filter. Since then we
have fabricated a shield to protect the air-filter from
the electric start, the motor now has to be kick started.
After 3 kicks the motor fired right up. Fortunately for us
this carb was jetted spot on and we only had to adjust the
idle screw in 1/4 turn. Since this was a new piston, we put
the motor through a couple of heat cycles at idle letting it
cool completely each time before we restarted the motor. By
this time we were all chomping at the bit to see how these few
simple bolt-on items would help with the overall performance.
After a couple of slow trips around the track to make sure
everything were working properly, we proceeded to put it
through its paces. Right away, I decided to pin the throttle
to see what kind of response it had. To my surprise, I was
fighting to try and find the rear brake to bring the front end
back down. This thing just hooked up and launched the front
end skyward, mine you, we are talking about a 200lb adult and
not a 70lb kid. Once we regained control, we opened it up, and
let me tell you, this thing flies for a 90cc machine. Every
adult that threw a leg over this machine was thoroughly
impressed by its performance. They could not get over how
responsive the motor and clutch system were.
the kids got all the adults off, it was there turn to play.
Once they had sufficient time riding around getting used to
the machines new power, we turned them loose in the sand pit
to see how much fun they could have. Hills that gave the stock
machines problems before, now were just little obstacles.
Words such as awesome, cool, great and it’s a blast were used
quite frequently to describe this machine.
final test was speed. After many searches on various websites
that post Drag Race results, we found that most of these 90cc
motors that are modded run in the low to mid 7 second range. We
figured if we could hit that mark we would be happy. Gears
were not available for the Alpha Sport so we decided to change
tires size to simulate a change in gearing.
was 18" Turf Tamers. In 300' the average time of 5 runs was
6.884 seconds with a 60' average of 2.197 seconds. Next we
proceeded to the stock tires which are also supposed to be 18"
but they actually measured 19" after we measured them. With
these tires on the average time in 300' was 6.726 seconds with
a 60' of 2.209 seconds. Now we bolted on a set of 21"
knobbies. Our test riders commented that they liked the feel
of these tires the best. The times also reflected what they
told us with an average of 6.635 seconds with a 60' average of
2.260 seconds. Our last tire that we bolted on was 22"
4-Snows. Although this is over kill for a quad this size we
were curious to see how the motor and clutch would respond to
these tires without any changes. To our surprise they really
didn't fair too badly. The 300ft average was 6.795 seconds.
Once the 300' times started going down we decided that was the
maximum limit that this motor could pull with the current
have an opportunity to get this motor to the last race of the
year. In live competition this motor was able to defeat the NY
State 90cc Mod Class Champion by making 2 consecutive runs of
6.715 seconds backed up by a 6.716 run in very poor track
conditions. By the end of the day it had turned faster times
then stock Raptors and DS650s.
conclusion we are very thrilled with how this motor prepped by
Trinity performed. It did everything it was supposed to and
more. The best part is that there is more to get out of this
motor in the future
if needed. For more details on this motor Trinity can be
3035 E. La Mesa
Anaheim, CA 92806
For Ordering: 1-877-FASTOYS
Information: (714) 632-3434
Fax: (714) 632-8484