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| I started this thread because I found a lack of post for this common problem on a John Deere 757 with a Kawasaki motor (fh721d-as04-r)
Keep in mind while reading this or trying these steps...I am not a professional and haven't worked on many motors. Always use the manufacturers suggestions and have a professional work on your stuff. (Unless you feel the need to get in too deep like me!)
I recently had my John Deere mower have a sudden loss of power. It was hard to start and when it finally did it had a loss of power.
Here was my trouble shooting steps:
1. Found a lack of power when I would engage the blades.
2. Thought I would check the spark plugs - good place to start.
3. They looked ok but one was a little darker than the other.
4. I also noticed that one plug was extremely hot and the other one was very cool.
5. I then knew that only one cylinder was firing.
6. One way I further tested it was pulled the cool spark plug (the one that wasn't firing) wire off while it was running. It didn't change the tone of the motor at all.
7. I then checked spark on ( I did this earlier when I pulled them but thought I would double check)
8. I then thought it wasn't getting gas. So I pulled the intake and carb- cleaned it.
9. Before I put it back on I thought I would also pull the valve cover on the troubled side. I thought it was a easy thing to check before assembling the rest of the motor.
10. When I pulled the cover I noticed that the rocker arms were off and the push rods were bent.
11. I took off the head and started to take out the valves. The exhaust valve was stuck.
12. The exhaust valve guide was pushed up towards the rocker arm.(I never noticed this till after I hit the valve down with a mini sledge)
13. I took the head to the dealer to have them find all of the parts that needed to be replaced.
14. They told me that the valve guide moved in the head and didn't allow the valve to move properly. They said that this is a very common problem with this motor.
They said I needed a new head among other things. One option that they gave me was to press the valve guide back down and reassemble with new parts.
These were the options they gave me:
1. Use old head with new parts $200ish
2. Use new head with new parts $300ish
3. Use new head with new part and a suggested new shroud(that is a fix Kawasaki added later) $400ish
I am really mad that Kawasaki doesn't give out this cover for free. They are the ones with the bad design. Sounds like a recall item.
Another reason I am very frustrated is because my father-in-law had they same thing fixed when he owned the mower. He spent $1600 to get the other side rebuilt. For the $1600 they didn't even put the new suggested shroud on the motor. That might have kept this side from getting too hot.
They say that the heat shroud that diverts the air from the flywheel around the cooling fins can become plugged with grass and over heat the head causing the valve to stick and move the valve guide. The new shroud has covers that can be removed to clean the cooling fins.
I am wondering what to do from here. I would really like to just get a new motor but the cost is too high...($2300 for a Kohler-without a cooling problem)
I would really hate to have the same problem later because I did do the $400 option they gave me.... Anyone have any suggestions??
I am planning to add pictures and maybe even make a YouTube video to show the problem and to show the reassembly.
I apologize for any spelling or grammar problems.. I typed this on my phone
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Bent push rods and stuck exhaust valve on John Deere 757 ztrak with 25 hp Kawasaki FH721D-AS04-R
