
03-2
SECTION 03 - ENGINE PREPARATION
ENGINE TUNING CAUTIONS
A few items to keep in mind when preparing your
engine:
– There are specific set of rules for racing, know
what those rules are!
– If your engine is operating at higher than stock
RPM, the rev limiter must be changed accord-
ingly. Never operate the engine without a rev
limiter.
– Sloppy engine building will usually result in less
power output.
– Follow the assembly and disassembly proce-
dures outlined in the appropriate model year
Shop Manual.
– Always use a laboratory blended fuel. Do not
add your own octane booster. Doing so will re-
sult in unknown burning rates of the fuel. Se-
lect a fuel with a given octane rating and tune
your engine to maximum efficiency for that fu-
el. (REFER TO OCTANE REQUIREMENTS FOR
ROTAX ENGINES).
– Correct your carburetor jetting to compensate
for engine modifications. Reconfirm correct jet-
ting at the race site. Atmospheric conditions
(ALTITUDE, TEMPERATURE, BAROMETRIC
PRESSURE and HUMIDITY) may be quite dif-
ferent at the race site or during different times
of the year.
Ignition timing may need to be altered from stan-
dard timing specifications to achieve maximum
power output if modifications are made to the en-
gine.
BASIC ENGINE TERMINOLOGY
MODEL YEAR
SHOP MANUAL
PART NUMBER
1989
295 000 060
1990
219 100 002
1991
219 100 004
1992
219 100 006
1993
219 100 008
1994
219 100 010
1995
219 100 013
1996
219 100 031
1997
219 100 048
Cycle
In a combustion engine, a cycle is
accomplished when the 4 phases;
intake, compression, combustion and
exhaust are complete.
TDC
Top Dead Center: The position of the
piston when it reaches the upper limit
of its travel inside the cylinder.
BTDC: Before Top Dead Center
ATDC: After Top Dead Center.
BDC
Bottom Dead Center: The position of
the piston when it reaches the lower
limit of its travel inside the cylinder.
BBDC: Before Bottom Dead Center
ABDC: After Bottom Dead Center.
Bore
Diameter of the cylinder.
Stroke
The maximum movement of the
p i s t o n f r o m B D C t o T D C I t i s
characterized by 180° of crankshaft
rotation.
Combustion
Chamber
Space between cylinder head and
piston dome at TDC.
Displacement
The volume of the cylinder displaced
by the piston as it travels from TDC to
BDC. The formula is:
= (
π
= 3.1416)
expressed in cc (cubic centimeters)
NOTE:
To transfer cc to cubic inches, divide cc by 16.387.
Compression
Reduction in volume or squeezing of a
gas.
Bore
2
Stroke
×
π
×
4
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Содержание Bombardier
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