I am just understanding that tricky concept myself, but I was wondering if any of you guys can explain it better that I know it. It seems to be important to engine wear and power. Anyone?

Help...please!

 

never heard of this combo thingie?

 

Longer rods will make the transmission of power from the piston to the crank more efficient. Unfortunately, longer rods tend to create a penalty at higher RPM by increasing the total reciprocating mass. The ultimate package would include the longest, lightest rod possible. For those of us running a 9" deck height, there are limits. A 2:1 rod/stroke length ratio would be great if it were possible.

Conversly, short rods are less efficient since there is a greater mass of the rod moving from side-to-side through the revolution of the crank. On top of that, the increased forces from this mass tend to wear rod bearings, piston pins, and even piston skirts faster.

I would be surprised if you ever found anything but an all-out race engine built for 12,000 RPM running anything with a rod/stroke length ratio of less than 1.5:1, and even that might be a push for holding together for a 500 mile race.