I have a five year old Z400 with a 48" deck that is woefully underpowered with an 18HP Kohler. The Z400 is the estate mower - a step up from the home model and slightly down from the commercial Z500s. I would like a bigger engine and see that a 23 HP Kohler two cylinder can be had for less than $800 over the internet. The commercial version of the same engine is about $1600. If you add the muffler, it looks like a straight replace. Has anyone done an engine replacement themselves and if so would you recommend it to a guy with lots of car engine experience? Are there any special tools that you would recommend? Would you recommend a different engine?
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