BOURKE CYCLE FORMULA

TABLE II
EXHAUST AND UPPER TRANSFER PORT SIZE RANGE BASED ON STROKE

STROKE EXHAUST PORT SIZE BASED ON 1 TO 0.2188 RATIO EXHAUST PORT SIZE BASED ON 1 TO 0.250 RATIO TRANSFER PORT SIZE BASED ON 1 TO 0.1875 RATIO TRANSFER PORT SIZE BASED ON 1 TO 0.1875 RATIO
0.250” 0.0547” 0.0625” 0.0469” 0.0500”
0.375” 0.0820” 0.0938” 0.0703” 0.0750”
0.500” 0.1094” 0.1250” 0.0938” 0.1000”
0.625” 0.1367” 0.1563” 0.1172” 0.1250”
0.750” 0.1641” 0.1875” 0.1406” 0.1500”
0.875” 0.1914” 0.2188” 0.1641” 0.1750”
1.000” 0.2188” 0.2500” 0.1875” 0.2000”
1.125” 0.2461” 0.2813” 0.2109” 0.2250”
1.250” 0.2734” 0.3125” 0.2344” 0.2500”
1.375” 0.3008” 0.3438” 0.2578” 0.2750”
1.500” 0.3281” 0.3750” 0.2813” 0.3000”
1.625” 0.3555” 0.4063” 0.3047” 0.3250”
1.750” 0.3828” 0.4375” 0.3281” 0.3500”
1.875” 0.4102” 0.4688” 0.3516” 0.3750”
2.000” 0.4375” 0.5000” 0.3750” 0.4000”
2.125” 0.4648” 0.5313” 0.3984” 0.4250”
2.250” 0.4922” 0.5625” 0.4219” 0.4500”
2.375” 0.5195” 0.5938” 0.4453” 0.4750”
2.500” 0.5469” 0.6250” 0.4688” 0.5000”
2.625” 0.5742” 0.6563” 0.4922” 0.5250”
2.750” 0.6016” 0.6875” 0.5156” 0.5500”
2.875” 0.6289” 0.7188” 0.5391” 0.5750”
3.000” 0.6563” 0.7500” 0.5625” 0.6000”
3.125” 0.6836” 0.7813” 0.5859” 0.6250”
3.250” 0.7109” 0.8125” 0.6094” 0.6500”
3.375” 0.7383” 0.8438” 0.6328” 0.6750”
3.500” 0.7656” 0.8750” 0.6563” 0.7000”
3.625” 0.7930” 0.9063” 0.6797” 0.7250”
3.750” 0.8203” 0.9375” 0.7031” 0.7500”
3.875” 0.8477” 0.9688” 0.7265” 0.7750”
4.000” 0.8750” 1.0000” 0.7500” 0.8000”

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