Four stroke leads two stroke! #14 KenLawrence (Honda
RS CRF150R) and #59 Garry Briggs (BBR Honda RS CRF150R)
both four stroke stalwarts lead two strokers Ron Carrick
Yamaha YZ85) and #93 Paul Borg (Honda RS85cr) at an Eastern Creek
What are your equipment
choices for a successful four stroke Motolite Race Bike?
So you've decided you've got the knowhow, resources and time to build a winning Motolite. Depending on how much work you intend to do yourself will dictate how much time you personally put into the project and have a bearing on the cost.
What chassis, engine, wheels etc to use, should it be two stroke or four stroke? The Motolite rules are pretty open except for capacity of four stokes being dictated by the valve count and whether water or air cooled.
For two strokes and for performance parity
with the four strokes the capacity is 85cc for
water-cooled and 111cc for air-cooled engines.
(Two stroke options are covered in an article "Winning
Motolite Capacity Rules
The performance parity of these different capacities and engine configurations have proven to be very close
in performance and lap times creating
competitive exciting racing for the Motolite
Engine capacities allowed in Motolite class:
- 85cc Water-cooled 2 stroke
- 111cc Air-cooled single cylinder 2 stroke
- 159cc Water-cooled 4 valve single cyl. 4 stroke
- 159cc Air-cooled 2 valve twin cylinder 4 stroke
- 175cc Air-cooled 3, 4 or 5 valve single cyl. 4 stroke
- 185cc Water-cooled 2 valve single cyl 4 stroke
- 190cc Air-cooled single cyl. Horizontal 4 Valve 4 speed gearbox (Laydown Motor)
- 230cc Air-cooled 2 valve single cylinder 4 stroke
These capacities are maximum sizes, a tolerance of 2% is included within these capacities.
The Motolite class is open to any grade of rider.
The choice of engine to be used can dictate the
chassis needed. We are only considering the four
strokes in this article. The following list is by no
means complete but covers engines readily available
here in Australia.
Suitable Motolite Engines:
- 159cc Honda CBR150 water-cooled 4 valve single cyl.
6 Speed Gearbox
- 159cc Honda CRF150R water-cooled 4 valve single cyl.
5 speed Gearbox
- 159cc Yamaha FZR125 water-cooled 4 valve
single cyl 6 speed gearbox (capacity increased to
- 159cc Aprilia RSV125 water-cooled 4 valve
single cyl 6 spd g.box (capacity increased to
- 190cc Daytona Air-cooled single cyl. Horizontal 4 Valve 4 speed gearbox (Laydown Motor)
- 230cc Honda CRF230F Air-cooled 2 valve
single cylinder 6 speed Gearbox
- 230cc Crossfire (Zongshen) CF230 Air-cooled
2 valve single cylinder 5 speed Gearbox
Suitable Rolling Chassis
Suitable chassis for the above list of motors can
be almost anything, but using one that works is the
trick for success. For a decent rolling chassis you can't go past
the Honda RS125 GP bike for it's handling and light
weight. This would be the ultimate
solution as suspension, brakes, weight and handling are all
sorted and full attention can be applied to the
motor and fitting.
However it may not suit all
the motors listed for instance getting the 230cc
engines to fit is a bit of an engineering feat but
it can be done. Trevor Lusby won a Motolite
championship in the not so distant past with RS GP
running gear wrapped around one of these engines albeit
in 185cc form as the rules dictated at the time.
Also with the four stroke engines the later RS125
chassis with vertical rear suspension unit has to be
used as the horizontal rear suspension unit in the
earlier chassis gets in the way of the taller
four stroke engines which means they won't fit. The
two stroke motors fit in the earlier frame as it was
designed for these engines in the first place.
CBR150 and CRF150R Engines
The CBR150 and CRF 150R motors sit well in the
later Honda RS125 GP
Chassis. Motolite race bikes with either of these engines
have had great success in the past winning the one
hour enduro many times and countless Motolite Championships.
Honda CBR150 Motor 150cc 4 valve twin cam
water-cooled 6speed gearbox.
Honda CRF150R mx motor 4valve Unicam water-cooled 5 speed gearbox
Which of these two engines to choose would boil down
to availability. There is little or no difference in
performance that is after they have been modified.
These bikes have proved a match for the Honda RS85cr
GP framed bikes with the right rider on board.
CBR150 engine can also be used in it's own frame or
in the CBR125 frame, wider rim wheels would be
advantageous but not essential if it's delaying your
Michael McLean ran a bog standard CBR150 to great
effect for a few years and had a lot of fun doing
Fuel injection is also an avenue that can be explored as seen here in Ken
Lawrence's Motolite which runs the CRF150R motor. However this is the exception to the rule, the carbies still rules
usually flat slide Keihins or Mikunis.
Yamaha YFZR and Aprilia RS4
For the Yamaha and Aprilia 159s these are
originally 125s with the capacity taken out to the
maximum 159cc. Usually these engines are used with
their original frames and running gear as they are
sold as reasonably well appointed sports bikes.
Being over the counter road bikes they will be a bit
heavier than an RS based machines but can still be an
very effective racer. The challenge is to shed as
much weight as possible.
Right: Jeff Brown hustles his much modified
Yamaha YFZ150 along to good effect.
230cc Honda CRF230F
230cc Crossfire CF230 (Zongshen)
The only real difference between these 2 motors
is the Honda has a six speed gearbox whilst the
Crossfire engine has a five speed. No real drama for
the five speed as
these engines have a abundance of mid range torque
and a six speeder seems almost superfluous. They
share the same bore and stroke (65.5 x 66.2mm) with
a lot of the parts being interchangeable. There is
plenty tuning bits available for these engines and
they can be made to go quite well. Again talk to the
tuners advertising on this website.
engine sells for around $640.00 brand new.
At this price it
leaves plenty of room for spending on go faster gear. With both
engines they would have to be modified, cam,
head work, exhaust and larger carburettor would be
the norm to get to the pointy end. Fuel injection is
also an option. Weight wise these
engines would be several kilos heavier than the 85cc
two strokes but would go some way to make up for it
with their meatier torque curve.
What chassis to use?
As mentioned earlier these engines can be a bit of a squeeze to get into
a Honda RS125 chassis, it can be done but it would
be best to check with any of the people advertising
on the website as they have done this previously.
Currently a Honda 210 cc engines is running in a
Suzuki RGV250 chassis the ex Bob Murphy bike now in
the capable hands of Clark Russell. Another
alternative chassis choice would be to slot one of
these engines into CBR125/150 frame which can be
picked up quite cheaply. Wider rims than standard
CBR125s would probably be desirable. There may be other frames
suitable read Aprilia Yamaha FZR125/250 KTM125 but
these haven't been tried.
For the other engines the 190cc Daytona engine
powered Supermono's have been having success
finishing second in the first round of the 2016 Sava
Tyres Bucket Nationals at the South Circuit at
Eastern creek and being regular visitors on the
When the Supermono is purchased it comes with a
basic Chinese 150cc motor which is uncompetitive
although it's quick enough to get some race
miles under your belt. The complete Supermono
with 150cc engine will set you back a mere
$1990.00 ready to go. Contact Nigel Begg on
0452 433 523.
To make this little gem (Supermono) competitive
you will would need to purchase the Daytona
Anima 190 four valve engine, it bolts straight
into the Supermono frame. Whilst out of
the box this engine is a lively performer, to be
really competitive in this class and as with the other
engines covered above the Daytona engine needs a tuners touch to
be seriously competitive.
You can sell the 150cc motor on to offset some
of the costs of buying the bigger engine.
The Daytona 190 air cooled motor has a
horizontal layout with four speed gearbox, four
valve head with roller rocker arms and bore 62mm
x stroke 62mm. The motor sells for $1399.00.
Download Engine user manual for
This engine could also be a candidate to slip
into a Honda RS125 GP chassis.
Michael Child aboard the Supermono190
finished second in the first round of the 2016
Sava Tyres Bucket Nationals at the South Circuit
at Eastern creek..
So there you have it!
This was just a run through some of the possible
combinations of engine and chassis available for
four stroke use in the Motolite class, you
may have other ideas of a winning combination. Don't
just keep keep thinking about it DO IT!
If your budget is tight we would suggest get your
bike built and ready for the track before spending
up on engine modifications. All of the above engines
have good performance standard out of the box and
would get you into the fray immediately. With a few
races under your belt and some experience of what is
required then turn your attention to getting more
out of your package.
Cheers see you at the track!
If you would prefer to go Two Stroke Click Here...
Open Rules. Phenomenal Racing