What's the Difference Between a 5.5 and 6.5?

[RobK]

What is the physical difference between the 5.5 (GX160), and the 6.5 (GX200)? I have to assume the the numbers mean 160cc and 200cc respectively. However the pistons and connecting rod are interchangable (I believe), so the bore is the same. The 5.5 has a smaller head combustion chamber, but that alone wouldn't make less horsepower. Is the difference the crankshaft stroke? Are the blocks the same? I have one of each to tinker with, and I'm curious.

 

[Oldschool]

About 1 HP and some stroke nearly identical in all other respects.....

The 160 block is slightly shorter than the 200 and the piston skirt is longer on the 160.

160s have 14 or 18 cc heads to compensate for the stroke