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Old 10-07-2012, 05:06 PM
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lotsagrass lotsagrass is offline
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Not again! More Kawasaki FH770D trouble

Unrelated to my last problem with the coils, I think....

I was having a problem with the engine sputtering under heavy load and I finally ended up replacing the coils and it once again ran perfect. It just so happens that only on my second time mowing since the coils were replaced, I hit a large rock while backing up (the rear of the deck caught it and pulled it up). The rock is large....maybe 2 feet long and 4 inches thick. It nearly stopped the engine while it was running at full speed with the blades engaged. Only a few seconds passed before I had the chance to turn off the blades. Once I turned off the blades and lowered the engine speed to idle, I noticed that it was sputtering, at idle. If I sped up the engine speed it seemed to go away. I continued mowing and it was strong and smooth from the best I could tell from my seat. When I was done mowing and I lowered the engine speed I noticed it was surging and sputtering again. I can only assume something happened mechanically to the engine when I hit that rock with the engine speed at full throttle and the blades engaged. Does that seem possible or is it just a coincidence? As you can see, when I pull the right side spark plug wire off at idle, it doesn't change anything at all, but it should be very noticeable when the plug wire is pulled off. If I pull off the LEFT side plug wire, the engine nearly dies. If I speed up the engine speed it's better, but it doesn't sound right. Any ideas? Valve problem due to hitting that rock??? Since the suspect side is on the side where the oil fill plug is, I reached my finger in to see if the valves were moving when the engine was turned over with a socked on the rear shaft and each valve does move but I can't tell too much since all I'm really doing is feeling if they're moving. I don't know how much they're moving and if it's the correct amount and correct time. This is very frustrating. If something happened to the engine after I spent all that time getting the coil problem fixed, I'm going to be really depressed :-( I don't know...maybe something odd happened with the right side coil like it's not in the position it should be in or something after that jolt from hitting the rock. I just don't know. Both plugs look the same visually and I even swapped them (they're both new too, after the coil replacement).

Here's the video. What do you think???
http://www.youtube.com/watch?v=cbc0fbjx6No
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  #2  
Old 10-07-2012, 05:42 PM
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lotsagrass lotsagrass is offline
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P.S. This engine and mower has around 175 hours on it and the oil has been changed at least 6 times since new so the engine is very clean and the exterior is always cleaned with a blower and an occasional wash.
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Old 10-08-2012, 07:16 AM
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lotsagrass lotsagrass is offline
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Watch the video

Here's the video again of the problem:
http://www.youtube.com/watch?v=cbc0fbjx6No

Is it possible that the right side could have a bent push rod, causing the valves to not open/close when they should? Let's assume it's not electrical since I JUST did replace both coils and plugs for a different problem. Could that abrupt slow down and nearly stopping of the engine at full throttle by hitting the rock cause a push rod to get bent? When I put my finger inside the oil fill hole/valve cover and felt the push rods, they felt pretty small and thin to me...maybe as a precaution to sacrifice a push rod in a case like this rather than causing more serious damage?

After watching the video, what are your opinions for what's wrong?

Also, I obviously have easy access to the rocker/valve cover and I assume the push rods would be easy to get out and replace, but I'm not sure about getting the rockers adjusted properly. I have the FH770D repair manual with all the info on how to do it but do you think this would be something I should attempt at home or just let the dealer do it, if the push rods are indeed what's wrong? I'm fairly mechanically inclined since my dad was a life-long mechanic but my only concern is making sure I get the valves/rocker arms adjusted right. I know it involves spinning the engine to the piston is in a certain position for the adjustments but really how difficult is that?

Last edited by lotsagrass; 10-08-2012 at 07:24 AM.
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Old 10-08-2012, 10:22 AM
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CLS LLC CLS LLC is offline
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It is highly unlikely that the abrupt stop caused any valve train issues, including a bent push rod. The valve train is only doing what the crank tells it to, weather the engine was turned off and stopped or stopped abruptly wouldn't make much of a difference to the valve train.

The abrupt stop could have possibly caused the timing gears to jump a tooth, all be it unlikely. The more likely option is you sheared the flywheel key which screwed up the ignition timing.

What you need to do is a compression check and a leak down test on both cylinders to find out if there is any mechanical issues. Once you do that then you can go from there. Assuming that is fine, replace the fly wheel key and enjoy your mower.

If you're feeling ambitious and/or don't have the tools to do a compression/leak down test, just pull the flywheel off and check if the key is sheared.
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Old 10-08-2012, 10:26 AM
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CLS LLC CLS LLC is offline
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After watching the video it appears as if you would have to remove the engine from the mower to replace the flywheel key. That being said, I would at the very least do a compression check. If you don't have a compression tester, you can borrow one from most auto parts stores with a deposit (often times for free.) Just don't tell them you are using it on a mower for which they sell zero parts for.
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Old 10-08-2012, 10:37 AM
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lotsagrass lotsagrass is offline
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Ok. But if there really is a bent valve, couldn't that also cause abnormal compression (low) readings?

I think I may just buy a compression tester so I have one handy.
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Old 10-08-2012, 10:46 AM
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CLS LLC CLS LLC is offline
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Yes a bent valve, or push rod would cause low compression. Poor valve timing (from a skipped tooth) would also cause low compression. You're not only looking for low compression, but in your case you're looking for a difference between the two cylinders.

If you buy one, try and find an OTC. Unless you're going to go with a matco, snap on, etc. Then OTC is the best affordable specialty tool manufacturer.

When checking compression make sure the throttle is fully open and crank it over 4 times. I don't know about an FH780, but an FH721V's minimum compression is 57 PSI

Last edited by CLS LLC; 10-08-2012 at 10:55 AM.
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  #8  
Old 10-08-2012, 11:12 AM
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piston slapper piston slapper is offline
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That rock didnt get close enough to the valves to bend them....
Check for loose or damaged wiring on the engine...
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  #9  
Old 10-08-2012, 11:15 AM
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lotsagrass lotsagrass is offline
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Sorry for all the questions. Just want to make sure I'm going about this the right way. Regarding the flywheel key possibly being sheared, wouldn't that only affect the timing of the spark since the magnets on the flywheel would be in a position they shouldn't be and not passing by the coils when they're supposed to? ...but not affect the timing of the valves opening and closing when they're supposed to? I mean, isn't the valve opening and closing totally dependent on the camshaft and has nothing to do with the position of the flywheel I'm showing below? Know what I mean? If my brain is thinking right, if the flywheel shown below is in the wrong position due to the key being sheared, then that would only throw off the timing of the spark, not the internal workings of the engine (crankshaft, camshaft, push-rods and valves). Right? Forgive me if I'm wrong and maybe I'm over-thinking it...but when I think about how the engine works, that's how I envision this working. So if the compression is GOOD (57 lbs that you mentioned is correct according to the FH770D service manual), then the flywheel key is a potential problem. If the compression is LOW/BAD, then the push-rods (bent) may be a problem. Make sense?



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  #10  
Old 10-08-2012, 11:17 AM
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lotsagrass lotsagrass is offline
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Quote:
Originally Posted by piston slapper View Post
That rock didnt get close enough to the valves to bend them....
Check for loose or damaged wiring on the engine...
Will do. I'll check everything just to be sure, but I don't know of any wiring under the mower anywhere...at least not that near the deck.

This was a huge rock that sort of wedged itself in the blades for a moment. It's probably 2 feet long and 4 inches thick and didn't break when hit. The blades look ok except for a nick and the spindles look ok and they still sound and look good too. Cuts well.
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