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Rotaxians rejoice! Pen has been put to paper,
and the first of hopefully many tech tips articles has been bestowed upon the
world of the FR125. The following is a compilation of many hours of testing,
months of scouring the Internet for scraps of information, and a ton of input
from SpeedQuest customers and fellow Rotaxians. This information is shared
with EKN readers in hopes that by doing so, Rotaxians will become better
informed, more knowledgeable, and more satisfied with their Rotax packages.
When dealing with the Rotax FR125, there are three basic areas that need to
be understood and paid special attention to. Those that take the extra time
to perform the duties listed in these areas will be rewarded with a lot less
downtime and fewer hours of frustration at the track.
Cleaning
The cleaner you keep everything on your Rotax, the easier it will be to
diagnose problems and rectify them. A clean Rotax (or any kart for that
matter), is a happy Rotax. Keep in mind you want to use appropriate cleaners
for certain parts though. For instance, the power valve bellows is made of a
pliable rubber. The condition of the rubber itself plays an important part in
the proper operation of the valve. Cleaning the bellow with an aggressive
cleaner, such as Simple Green, could weaken the rubber and cause it to
"blow off" the piston a lot easier. Thus, we recommend using only
mild soap and water for cleaning the bellows. When cleaning the carburetor
parts, i.e., jets, floats, filters, etc., you should use a carburetor
cleaner. To clean any brake component you should use a good quality, fast
evaporating brake cleaner. All of these items are really common sense, but
most of the time, problems could have been prevented with proper cleaning to
begin with.
Carburetor
With the Rotax package the biggest issue people have is normally with the
carburetor and the 'mystery' involved with adjusting it. Because the system
uses a "fixed" jet system, jet changes are necessary on a daily
basis (sometimes hourly) and in a lot of cases those changes are critical to the
proper operation of the motor. We will address that in a little more detail
further on, but the big thing to remember here is still, keep it clean. Many
of my customers complain of a bog during turns, or after letting off the
throttle. The float will operate the needle & seat and if incorrectly
adjusted, can cause a seemingly untraceable bog. To correctly set your float
levels do the following:
You must remove the carburetor from the motor to gain access to the floats.
Turn the carburetor upside down and remove the float bowl. Make a note of how
the floats (white plastic pieces) are positioned in the float bowl cavity.
Continuing to hold the carburetor upside down, examine the float lever.
The prongs of the float lever should be parallel with the base of the carburetor.
If the prongs are not level, DO NOT BEND THEM!!! You adjust the prongs by
bending the small flap that sits on top of the needle and seat. Bend this
flap until the float prongs are absolutely level.
Now that you have adjusted the floats to their proper position, we need to
set the clip appropriately. To begin, set the slide needle at its richest
point. This is done by removing the small 'e' clip and setting it at the
lowest groove on the slide needle.
NOTE: Visualize this: As you move the clip lower on the slide needle, it
raises the height that the needle sits at in its resting position. This
allows more fuel to enter the carburetor, thus it is making the system
'richer'. Conversely, if you were to raise the clip to a higher groove, this
would allow less fuel to enter and thereby create a 'leaner' condition.
Next you will need to install the proper Main Jet for the current conditions.
Remember that the proper main jet can only be determined by knowing all of
the following conditions:
Temperature
Humidity
Barometric Pressure
Altitude
Once the Main Jet is installed and the carburetor reassembled, you will be
ready to install it back on the motor. Be sure to tighten the hose clamps and
that all of the bolts are tight as well.
Take the kart out on the track and observe proper 'warm-up' procedures. Once
the engine is warmed up, begin pushing it to its limits.
LOW RPM TUNING - If the kart runs rough at lower RPM's (5,500 - 8,500), we
need to adjust the needle setting to be 'leaner'. How 'rough' it is running
should determine this adjustment. Never adjust more than (2) grooves in any
direction, this can cause a low RPM seizure.
HIGH RPM TUNING - If the motor will not rev cleanly from 10,000 RPM through
to 12,500 then change the main jet to ONE jet lower. For example, if you are
running a 168 jet and the motor pulls well through 11,500 and begins to break up or bog at 12,000 you should change to a
165 main jet. If the leaner jet seems to help, but still does not feel 100%
right, consult your plug reading to determine if a leaner jet is suitable. BE
VERY CAREFUL. At this point, going too lean could cause an engine seizure.
Once you have found the appropriate main jet, it is possible you may have to
change the clip setting to eliminate any lower RPM bog.
If the 'leaner' jet does not remedy the problem, you should install a jet
that is one size bigger (richer).
The indications of a jet that is too lean can include a loud 'popping,' or a
sudden drop off in performance at high RPM.
Any time the jet seems too lean you should consider immediately coming in to
the pits, getting a good 'cut' on the plug and reading your plug indicators.
Electrical
Too many Rotaxians are not aware just how
important the electrical system is to proper operation of their kart. The
Rotax FR125 operates using at 'total loss' ignition system. This means that
there is no on-board charging system, and that the ignition system relies
solely on the battery for power to supply the ignition coil. This also means
that if the battery does not have adequate power, the ignition coil will not
function properly. As a result, it is VERY important that you ALWAYS keep
your battery at full charge.
The FIAMM GS battery is a sealed lead-acid battery. It is not a Ni-Cad, nor
is it a Nickel Mh battery. As such, it needs to be charged like any other
lead-acid battery. This battery does not have the type of memory that is
associated with the Ni-Cad or Ni-Mh. If the battery is ever fully discharged
there is a good chance that it will be damaged. The damage may not even be
apparent immediately, but the lifespan of the battery may shorten
significantly. At SpeedQuest, we've have had several batteries last over one
year. Conversely, we have had batteries that seemed to last only 2 months.
Without a doubt, it is in your best interest to avoid jarring the battery
unnecessarily, or dropping it as either of these can dislodge the internal
components and cause a short circuit.
The battery should be placed on the approved charger anytime that it is not
being used until about two to three hours beyond the green light
illuminating. Because of the nature of the beast, it is very advisable to
have at least one spare battery that is fully charged. This is probably the
quickest and easiest item to change on the kart, and should be your first
adjustment in any situation where the ignition seems to suddenly cut-out or
misbehave.
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