Kawasaki FH721 rebuild

scott2013 · May 21, 2015

I've got a JD 757 Z-mower with 420 hours and a wore out engine. I bought this mower used for cheap $$ knowing the engine needed attention. I've got it tore down and found the major problem is the crank shaft and rods. It looks as if the engine got hot at some point (common on this model) and did some damage. The pistons look OK and mic out to spec as do the cylinders. I'm thinking I'll replace the crank, rods, pistons, piston pins & rings. Should I hone the cylinders and if so what grit hone would be recommended? The total cost of a rebuild is about $550 and a new engine is about $1900 (more than I paid for the mower) so a rebuild seems to be the way to go. Any feedback is welcome.

Scott

T.R.K. · May 21, 2015

Which engine does it have? Not familar with that model and I don't know whether you have a Kohler, Kawasaki, Air cooled or Water cooled.

FYI: certain Kohler Command engines had extra hard cylinder liners and Kohler does not recommend honing them. (The manual does not say why not to do this, but my guess is that the hone marks in the extra hard liner will wipe out the oil rings prematurely and it will always use lots of oil.)

As far as your plan goes, I second replace all those parts. Also be sure to lap/seat the valves and inspect the camshaft and compression release very closely.

scott2013 · May 21, 2015

The engine is a Kawasaki FH721 which is a 25hp V twin. I've been searching the net for info and the best I could find was to use a 400 grit stone hone (not the ball type). The results were a fine stone broke the glaze and showed any wear in the walls but didn't put deep crosshatch into the cylinder which caused premature ring wear. Don't know if this is fact or fantasy but it sounds reasonable.

Scott

Kawasaki FH721 rebuild

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T.R.K.

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