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Old 07-24-2012, 08:28 PM
sadie123 sadie123 is offline
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Location: sioux city, ia
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F525 540pa engine die, low compression

Dear Restrorob or anyone else that was at try!!!!!!!!!!!!!!!!!!!

I used to read alot of your thread responses on this website haven't been here in awhile. I have work on several small engines, but I am pulling my hair out on this one. This is a F525 John Deere unit has a 17 hp kaw on it. Believe it is PA540. This is the unit with the engine and tranny all in unit.
This unit has 750 hours on it. The unit was running fine I was told then it started to sputter on a incline. States the mower started to smoke then it came out of it. It then died 15 mins later. She stated it was low on oil so they added alittle. I can see it is clean fresh oil in the dipstick, and still alittle low. Not usually a good sign..
Unit has spark, it does have fuel (Fresh). It will back fire through the exhaust and intake when trying to start. The only way to get this unit to start is to keep the unit turning fast enough with the starter to finally get to run. Then dies when you get it back to idle speed, but it take an awful lot to get it started. Sometimes it will no restart.....
I noticed it had little compression by the way it turned over. I did a compression check 45psi. Should have 71psi min, due to compression release. Compression release is on the exhaust side of the camshaft.
I then took notice of the spark plug and all of the cooked oil on the electrode. I then squirted oil in the cylinder and took another test. Same 45 to 50 psi. I then took off valve cover and checked adjustment, was .010, was supposed to be .006 reset valves. Checked the height of the exhaust and intake springs. I have seen these unit spit out the valve seat before. They looked fine same heights as each other. ?? Low compression, fires out exhaust and intake. I removed the flywheel to make sure the key wasn't sheared, or sheared alittle causing this. No, good there.. I then removed the coil and ignitor due to it seemed to fire at the wrong time, but I know, i still had low compression. I tried a good test coil and ignitor, at the same time, no start, same thing, fires out exhaust and intake.
I couldn't resist, I pulled the head on this unit. The cyinder surface was very smooth and had no cross markings, piston was tight throughout the hole. very little side to side play at any point. The seats where in good condition. I could see the exhaust valve was leaking some due to blackness on the face of the seat and valve, no pits. Head surface was fine and valves were tight in guides. Cleaned all parts and lapped valves back in. replaced seals, head gasket and torqued to spec. I am back to the same problem. 45 to 50 psi I have checked the compression release by watching the valve open just before t.d.c. I have done things I think I have forgoten to mention. Any thought or things I have missed. Is it possiable that the engine got low enough on oil that it slipped the timing gear a hair??? Wow what a job to check this.. This is driving me crazy any ideas are greatly appreciated. Thank you,,,,

Last edited by sadie123; 07-24-2012 at 08:33 PM.
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Old 07-25-2012, 06:31 PM
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Restrorob Restrorob is offline
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sadie123,


You've done everything I would have tried except a cylinder leak-down test from the start, I'm familiar with this machine as one of my customers own one. I've decided long ago that if for any reason that engine needs a tear down it won't be by me !

Since this job is a PITA, I'd suggest a cylinder leak-down test. This will show for sure the valves are fully closing and the condition of the rings, Putting oil in a cylinder laying on it's side isn't a very good test since little to no oil will get to the top of the piston/rings to help seal.

I've only seen one Kawi which was a twin jump time, It peeled the teeth off 1/3 of the cam gear. Once it did that the cam didn't rotate to open the valves.

You have to determine why the compression is so low, If it's the rings then the rest of the internal components can be inspected while tore down.....

Best of Luck ! I feel your gonna need it.....
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Old 07-25-2012, 07:10 PM
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dutch1 dutch1 is online now
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Rob, I had to wait for the three spinning dials to come up lemons in order to realize the unit under consideration. Only saw one of those while I was in the shop and that was one more than necessary. The guy that owned it was deaf and couldn't speak--all service was arranged by passing written instructions back and forth across the counter. The guy loaded and unloaded on three planks and was backed into a Ford Ranger with the deck resting on the tail gate. I recall the shop owner saying that if it was coming in for anything more that a PM service it was going to Deere--so I can certainly understand your comments.
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Old 07-25-2012, 08:48 PM
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piston slapper piston slapper is offline
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Is this an fc540 or an fh500....
Sounds like a broken ACR or a bad woodruff key on the crank gear...
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Old 07-25-2012, 09:45 PM
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dutch1 dutch1 is online now
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Slapper, I'd say it's an fc540 since many of the 540 listings are proprietary to the equipment manufacturer--something JD is well known for.
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Old 07-25-2012, 09:50 PM
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Quote:
Originally Posted by piston slapper View Post
Is this an fc540 or an fh500....

Slapper, It's like a FC540 but the hydro units are made as part of the crankcase sump/pan.....

sadie123 said the exhaust valve was being bumped open just before TDC, The last FC I was into that had a broken ACR built too much compression. The starter wouldn't spin it over compression stroke like valves being out of adjustment on a Briggs Intek.....


Guess I need to type faster Dutch !
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Old 07-26-2012, 12:15 AM
sadie123 sadie123 is offline
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I know the compression release is working fine. . But you are right I have seen them breakto the compressure release before but not on this model.. The twins cylinders were good to break the camshaft do they are plastic...Iam going to the cylinder leak down test tomorrow morning... I do believe it is the woodruff key on the crankshaft.. I had to laugh at your guys responses to the f 525.. We sold hundres of those when I worked for deer.. They worked goodl great but they're tough to work on......everything u do u have stand on ur head to do.i have a customer that is deaf and he rides his mower to my place and we pass notes on the repairs..small world huh... thanksfor all of ur help..if it passes the leak down test I guess I'll get started tearing it apart..what a PITA..........will let u know..
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