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Frequently Asked Questions
 | What do the letters MSD
stand for? Multiple
Spark Discharge.
It's a patented design that fires the spark plug multiple times every time
the unit is triggered.
| What will a MSD unit do for me?
Easier starts, more horsepower, better throttle response are the expected
results from a MSD capacitive discharge ignition - whether it's an analog or
digital system.
| Why do I need more ignition
power? With the multiple spark discharge of a MSD
ignition, it is finally possible to completely ignite the air/fuel mixture
in the cylinder - giving you more horsepower. In a 2-stroke engine this is
important. When you suddenly give the engine "the gas" after
idling, the engine will bog down. This is the result of a weak stock
ignition trying to burn off the excess fuel that has built up in the
cylinder. The stock ignition's weak spark can't do the job. A MSD ignition
has a hotter spark to start with, and along with the multiple spark
discharge, a MSD ignition will thoroughly ignite the air/fuel mixture.
| Spark Plug Gap
With a MSD Ignition you can run a wider spark plug gap than you
would be able to with a stock ignition. The MSD Ignition has a higher
voltage output and can jump the spark plug gap easier. As an example, if you
normally would run a .028 inch gap on your spark plug with a stock ignition,
you could run a .032-.034 inch gap with a MSD Ignition. There are variables
that will affect the gap size: the higher the compression - the smaller the
gap; the hotter the output of the ignition - the larger the gap, etc.
| What does "Total
Loss" mean? The flywheel no longer charges the
battery. Usually the flywheel on a total loss system has been replaced with
a light weight aluminum flywheel, without the charging magnets. Quicker
acceleration is the main advantage of a total loss system since you have
lightened the moving mass on the end of the crankshaft. The drawback is that
you have to keep an eye on the charge level of the battery - and how often
depends on how many times you use the starter (a big drain on the battery)
plus how long you are out on the water. Figure about 4 to 6 hours of ride
time starting off with a fully charged battery that has a 17 amp-hour rating
- depending on how many times you use the starter.
| How do I find Top
Dead Center (TDC)? TDC is where the piston has reached its
highest point in the cylinder. It is the foundation to accurate timing. To
find TDC, remove the spark plug and use a plunger depth gauge to judge where
TDC is. If you don't have a depth gauge, place a screwdriver thru the spark
plug hole until the screwdriver rests on top of the piston. Turn the
flywheel until the screwdriver reaches its highest point, make a reference
mark on the flywheel and a reference point on the case. Then reverse the
rotation of the flywheel, allowing the screwdriver to lower down and come
back up again to its highest point. Make another reference mark on the
flywheel. If the two points match up - consider yourself lucky because you
have an accurate crank/connecting rod/piston assembly. If the two marks
don't match up, pick the point exactly between your two reference marks
(using the points closest together) - this is true TDC.
| Analog vs.
Digital Ignitions Why the switch from analog to digital?
The main advantages of a digital ignition are: accurate timing; smaller
ignition box size; full access to the timing curve via dip switches; you can
change the initial timing at the MSD box electronically instead of moving
the trigger around physically; reliability (because there are fewer
components to fail).
| Can I get replacement instruction
sheets? Yes. You can download instructions in the instruction
section. We can also mail them, or fax them to you. All we need to know
is the part number of the unit that you need replacement instructions for,
and we'll be happy to get them to you.
| What is RF
noise? RF Noise stands for Radio Frequency noise. It is
generated by spark plugs when they spark, and on motorcycles by points. RF
noise causes CD ignitions to run erratically if they aren't shielded. A good
way to lower RF noise is to use a good set of RF suppression spark plug
wires - like MSD's 8.5 mm Super Conductor Wire or our 8mm Heli-Core wire.
The Super Conductor uses a special winding procedure with a Ferro magnetic
impregnated center core that is an effective RF suppression spark plug wire.
In addition to using good spark plug wires, make sure that all grounds are
good and clean. If you still have RF problems, shielding the ignition or
moving it away from the RF source helps reduce interference. |
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| Why don't I have spark?
In most cases, it is usually due to a bad ground or no ground at all. Check all
connections. Here are a few things you could check: make sure the ground
wire is securely attached; that there is no paint under the ground wire; the
connectors have good secure connections; there are no breaks in the wires;
the battery is fully charged. Check for a bad on/off switch to the ignition
box. You could have a bad coil, and switching it out for a coil that you
know is good is the fastest way to determine whether a coil is the culprit.
Perhaps you have a bad triggering device. Check it by
removing the spark plugs (leaving the spark plug wires on), and grounding
them to the engine. Next: clip the two green trigger wires coming out of the
engine, and repeatedly touch the 2 wires going to the ignition box together.
Make sure the power to your ignition is on. You should get a spark, or the
L.E.D. (if equipped on your MSD box) should light. If you get a spark, then
the trigger is bad. If the L.E.D. light turns on and there is no spark -
then either you have a bad coil, a bad spark plug wire(s),
or a bad spark plug(s). |
| How does a Rev Limiter work?
A rev limiter does just what its name implies: it limits the revolution
speed of the engine. Why is this important? If you have the throttle wide
open on a watercraft and it comes out of the water, there is no load on the
engine. The engine will dangerously zoom up in speed past its intended
design and physical limits, possibly destroying itself. On a motorcycle if
you have the throttle wide open and miss a shift, the same thing happens: a
rapid increase in rpm's, possibly destroying parts. A rev limiter is placed
in the electronic circuitry that prevents the engine from over-revving. At a
pre-set rpm - say 7,000 rpm - the rev limiter engages. Once the engine
reaches 7,000 rpm, it interrupts the signal to the coil, alternating on/off,
slowing the firing sequence, and preventing the engine from rapidly shooting
up in rpms. Factory rev-limiters are generally set at low rpm levels. If you
have modified your engine you may not notice any performance gains due to
the stock rev limiter's low rpm limit, which is why you would use a MSD Rev
Limiter. With our units you can set the point, where you want the rev
limiter to limit the engine's rpm.
| Does a Rev Limiter automatically
make my engine go faster? Only if the engine is currently
being held back by the factory rev limiter. You never want to set the rev
limiter's rpm cut off point too high - serious engine damage could occur. |
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| How Do I Program It?
Whether for motorcycle use or watercraft use, each MSD Digital Ignition is
optimized for the particular vehicle. Obviously, a full technical
explanation of correct ignition timing for each individual engine would take
up too much room here. A broad overview of how to arrive at a timing
curve is shown in the guide below. |
| FACTOR |
ADVANCE FOR |
RETARD FOR |
| Cylinder Pressure |
Low |
High |
| Engine RPM |
Low |
High |
| Energy of Ignition |
Low |
High |
| Fuel Octane |
High |
Low |
| Mixture (Fuel/Air) |
Rich |
Lean |
| Temperature |
Cool |
Hot |
| Combustion Turbulence |
Low |
High |
| Load |
Light |
Heavy |
You need to have all systems operating properly
before you can fine tune your ignition system. Here are a few tuning tips for
watercraft and motorcycles.
| Reading spark plugs is an important element
of tuning. Take a good look at the insulator's ceramic coloring.
| A good light tan/gray color is perfect.
| If the plug is black with wet or dry
deposits, it's usually a fouling problem. Heavy dry deposits might indicate
too rich a carburetor(s), too cold a plug heat range, low compression,
timing is retarded too far, or the gap is too big.
| If the deposits are wet, it could be due to a
blown head gasket, bad rings or valve train problems, or too rich a carb
setting.
| Silver specs, black specs, melting, or
breakage at the firing tip on the plug is a sign of detonation.
| A white or real light plug color could
possibly mean the carb(s) is too lean.
| Spark plug color is only accurate when
checked after a high speed run, engine turned off at max rpm, and craft
glided in with engine still off. No idling allowed!
| Each cylinder should be fine tuned as a
separate motor/pipe/carb combination. Not all carb screws on multiple carb
set ups will necessarily be adjusted the same - or jets necessarily the same
size. |
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All parts sold by MPS are for off road closed course use. They are not intended for use on public streets or highways.  Motorcycle Performance Specialties
5350 McIntosh Point #132 - Sanford, Florida - 32773
Phone: (407)330-9727 - Fax: (407) 322-8632
Sales E-Mail: sales@mpsracing.com
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