Kohler CH730 loss of power

Remove the muffler or at least loosen the exhaust flange bolts. Run it up to see if it continues to pull properly. If so, your muffler is being restricted by a collapse inside. Doesn't happen often in the mower world. However, it does happen.

I actually tried running it briefly without the exhaust on to see if there is indeed a blockage and didn't change anything. There is also plenty of pressure coming out of exhaust.
 
I actually tried running it briefly without the exhaust on to see if there is indeed a leak and didn't change anything. There is also plenty of pressure coming out of exhaust.


Not sure if this is advisable, but seems like if you could play with the linkage while simultaneously bogging it down you could check the governor?
 
One thing that hasnt been mentioned yet are your blade bearings. disconnect belt and make sure each blade spins easy. There should be no side to side play. Also double check the valve lash on both cylinders. Also you could try taking your carb intake off and check the intake port of the heads. Bad gas over time will build up a honeycomb of corrosion that will rob power.
 
Since this engine doesn't use compression release your readings of 130-135 are low according to what Kohler list in the service manual for this engine. Kohler says 160 should be the mininum, so I think I would be looking into a leakdown test next to try to find the cause of the low compression. This engine doesn't have adjustable valves because of the hydraulic lifters, and if one of the push rods had come out it would be running on one cylinder and when you removed the spark plug from the good cylinder the engine would of died. So I don't think it is a valve issue but may want to pull the rocker covers and rotate the engine through a couple revolutions to make sure the valves are opening about the same amount to rule out cam lobe lift wear.

Something else to consider is a partially clogged main jet in the carb, since the engine only uses that jet when the deck is engaged and the engine is under a load.
 
I agree with I’ll, about checking the main jet. Another thing I would check is, What RPMs are you running at? I set those engines at a minimum of 3200. If you can give us a better picture of what is happening. You say loses power under load. What type of load, when you kick in the PTO, normal mowing, heavy grass, going up hill PTO off? Do you operate the unit at full throttle when cutting? Remember we are not there to see what you see and hearwhat you hear. The better the picture you paint, the better info we can give you.
 
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