Carburetor Main Jet Connection Chart - BOMBARDIER 1996 Ski-doo MX Z440 Handbook

Section ENGINE PREPARATION
04
A01C47S
Example : With a 250 stock main jet, at an altitude of a 600 m (2000 ft) and a temperature of -
5°C (20"F) :
CAUTION : These values are guidelines only. Specific values/ adjustments vary with
temperature, altitude and snow conditions. Always observe spark plug condition for proper
jetting.
This table is more than adequate for stock engines. Two-stroke engines with high specific outputs
that are heavily modified (twin pipes, high compression, large carburetors, etc.) and performing at
high RPM are very sensitive to air density changes. The following is a very accurate formula for
correcting jetting.
First, a baseline for jetting must be established.
Jetting, horsepower, and B. S.F.C. data can be obtained with dyno testing but also confirmed with
field testing. The tried and true method of determining mixture ratio is to inspect the parts of the
engine that are directly exposed to the combustion process. The two best indicators are the spark
plug and the piston dome. The color and where it is located are the two things to look for.
Chocolate brown on the insulator, ground electrode, and piston dome indicate a proper mixture.
The ground electrode should show a difference in color just at the radius of the electrode.
04-50
CARBURETOR MAIN JET CORRECTION CHART
FT / METER
-40 /
-60 f
-50 -40
111.10 107.40 103.70 ,Ofoo
0
2000 I
105.77 102.07 98.37
600
4000 I
100.43 96.73
1200
6000 f
95.10 91.40
1800
8000 I
89.7 86.07
2400
1000 I
84.44 80.74
3000
= 227; use 230 jet.
100
o
"F J "C
+20 I +40 / +60 f
-20 / -o I
-20 -5 -5 -15
-30
92.60 88.90
96.30
94.67 90.97 87.27 83.57
93.03 89.33 85.63 81.93 78.23
87.70 84.00 80.30 76.60 72.90
82.37 78.67 74.97 71.27 67.57
77.04 73.34 69.64 65.94 62.24
+80 f
-25
85.20
79.87
74.53
69.20
63.27
58.54