Piston and cylinder extent determines displacement.
Bore
The Muzzle is the interior dimensions of the cylinder. On the 72 cc Honda, the Muzzle is 1.85 inches, and on the 99 cc the Muzzle is 2.09 inches. This resources the preferable Engine can compress a higher volume of fuel and air concoction than the smaller one.The Honda CRF 70 and 100 are both starter bikes for fresh riders. Both are single-cylinder, four-stroke motors. Both are air cooled. The differences are establish inside the Engine.
Stroke
The stroke is Until when the piston pushes the air, or the distance that the rod moves the piston in the cylinder. The smaller Engine has a stroke of 1.63 inches, and the Honda 100 has a stroke of 1.77 inches. Thus the compression ratio on the 100 is higher also.
Cylinder Heads
Because the larger engine has a higher volume, it needs larger intake and exhaust valves to handle that volume. The Honda 100 must handle 6.05 cubic inches of mixture, and the Honda 70 handles only 4.4. Therefore the cylinder heads have a slightly different design also.
