Changing a Lawnboy "C" series engine to "D" series piston and cylinder?

Changing a Lawnboy "C" series engine to "D" series piston and cylinder?

It is my understanding that one can change a "C" series engine to a later "D" series piston and cylinder. From what I have read, one has to also change the connecting rod. My question is, with a "D" series connecting rod, piston and cylinder, is that ALL? Will the "D" series con-rod fit the "C" engine crankshaft?

Re: Changing a Lawnboy "C" series engine to "D" series piston and cylinder?

Phototone said:

It is my understanding that one can change a "C" series engine to a later "D" series piston and cylinder. From what I have read, one has to also change the connecting rod. My question is, with a "D" series connecting rod, piston and cylinder, is that ALL? Will the "D" series con-rod fit the "C" engine crankshaft?

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Yes the D series connecting rod will fit the C engine crankshaft just fine. The rotating assemblies of a large bore C and a D400 series are basically the same, along with the cylinders as well, the only difference is the crankshafts. The C series drives the points to open and close using a cam ground into the crank, whereas the D series uses a hole to mount the spark advance cam and flyweight that drives the points to open and close. My 5024, which is a D400, was restored using a large bore NOS C19 short block, all that was required was to use a D series crank, which I happen to find a NOS crank for it and it was good to go. I would recommend that anytime you go from a single bearing crankcase to a dual bearing crankcase that a new crank be used so that the lower seals will not be chewed up with the roughness of the old crank.