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Discussion Starter · #1 · (Edited)
We have a John Deere D100.

A month ago we did the yearly maintenance, cleaned the corroborator, replaced the spark plugs and fuel filter bought a new battery. The John Deere ran fine after this until yesterday. The engine cranked but would not start. We replaced the spark plug again after noticing the old had some oil on it. Not sure if the oil got on the spark plug though from the diagnostics because it was not a ton. After replacing the spark plug the John Deere turns on but makes a thudding noise and blowing white smoke. We ran the engine for minutes and the smoke and noise did not go away. We hadn't replaced the oil this year so we drained the oil and refilled but the same thing happened. If we adjust the throttle the engine practically turns off when the throttle is low. We suspect it could be the flywheel key but need to get more parts to actually inspect it and we are going to get a spark plug gap but we have to order online and wait for these to come in. Is there any other things we should look into to repair based on this info? Any help would be appreciated.
 

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You need a head gasket.
That is possible. White smoke means oil is getting into the combustion chamber. There are several different ways it could be getting in there, leaking head gasket is a likely contender.

A leakdown tester is the tool that will give you a better idea of where and how much the combustion chamber is leaking.

The thudding sounds could be a clue that it is the head gasket. Removing and replacing a head is probably not the best first small engine repair job to tackle. I don't think it is too hard to do, but there are lots of steps that need to be done correctly to get it to be better/right.

How old is the engine and how many hours?

If you really like the mower and want to tackle fixing it yourself, there are lots of people here who have done it before (and quite a few threads here) that will be glad to help. There are also lots of videos on YouTube. I like Taryl fixes all
 

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Be aware that just because you have watched one (or even 10) videos of someone doing something, doesn't mean that you will actually be able to do it as fast, easily, and/or as well as the person on the video. They frequently leave out some parts and/or they know what to do when something doesn't go the way it is supposed to, which is more frequently than most would like.

But, if it's not working now, you do have a little less to lose, since it still won't be working if you make a mistake. It just might make it harder for someone else to fix it right. Or, you might get to learn how to replace an engine, which might be easier.

So, do you want a learning experience, or just want it to work?
 

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Discussion Starter · #5 ·
Thanks for the information. We are typically do it yourself repair people so completely understand videos can leave things out but we are newbies with engine repairs. Its a 9 year old mower with 53 hours of use on it. We more just want the lawn mower to work so if its better to get repair help we are willing if this sounds like problem beyond a diy repair.
 

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53 hours is not a lot. 9 years is, but even with no oil changes, as long as it had enough oil, it should have been okay.

Is it new to you, or have you had it since new?

What maintenance have you done to it over the years (be honest, no judgement here)?

I would start with the simple things first. Does it have too much oil in it?

Can you hear where the thudding sound is coming from? It could be a hole in the exhaust or muffler. That would probably be easier and cheaper to fix.

I did a leakdown test on my X300 a couple of weeks ago. I didn't open the oil fill valve before I did the test and oil spewed out the breather into the air cleaner. It made a huge mess. I was unable to clear out all the oil from the carburetor, so it smoked like a serious fog machine for at least 10 min before it got most of it cleared out. The leakdown test indicated the engine was fine (almost new at about 2% leakage). I can't explain why that much oil came out on the test. Maybe the breather filter/chamber needs cleaning. Maybe the constant high pressure was too much for the breather system to handle. I just wanted to know that my tester was working right. Now I am still not 100% sure, since all my engines test like new, and some have 300-400 hours on them. But, the tester is working as far as I can tell.

If you know a good honest small engine mechanic that you trust, they can give you an idea of what might be wrong.

The leakdown test will tell you where stuff is leaking. You can hear the leak. You will have to take off the valve covers to get a good idea. Be prepared for dealing with stuck gaskets that can be a pain to remove. Removing them can damage stuff, but many people are capable of dealing with this issue. It just takes time. Depending on the availability of a mechanic, it could take more or less time to go that path. It will probably require more dollars, but sometimes it is something simple and a trained professional can fix it faster and cheaper than someone that is "learning on the job".
 

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I would recommend you obtain a shop manual prior to tearing the motor. The job is much easier if you have a step by step guide for disassembly and assembly.
 

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Discussion Starter · #8 ·
We have had the John Deere since it was new.
Maintenance:
I honestly can't remember if I did 1 or 2 oil changes < 50 hours
Replaced air filter once
Replaced oil filter once
Replaced battery 3 times
(First oil change I know it was closer to the top of the dip stick than the bottom, so possible it was slightly over but ran for many years after this)

Around 51 hours
new fuel pump,
new battery,
cleaned carb (although it looked spotless to me),
new spark plug,
greased all joints
Spray lubricant where I think the instructions say (this was hard to find)

Around 53 hours mower started fine but after maybe 10-20 feet it started sounding sluggish and just sputtered and turned off. After this it wouldn't start. I think a little dried grass fell off and the blades hit it, didn't think it was hard enough to break flywheel
Broke spark plug trying to take it off to double check things.
Tried to get a look at flywheel but don't have right socket size.
Checked fuse at least looks good.
Trickle charged battery
Waited 24 hours then:
New spark plug this caused it to start but white smoke and thumping so I (prior to new oil it was fairly close to full on dip stick but wasn't over the line)
New Oil, and Oil filter (oil was almost right in the middle of dip stick (used whole bottle of john deere oil)) I can double check this after it settled


So don't think its too much oil as it has done same on two oil changes.
I do not know where smoke is coming from I can check that tomorrow.

Also the john Deere has been kept in a connected garage for first 7 years (so extreme temperatures should have been kept to a minimal). After that was stored in shed year round.
 

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If it is starting without the engine reaching a point where it seems like the battery is dead ( does not want to spin fairly freely) and it is not backfiring it is not the key...you should confirm with a leak down test or compression test, but you need a head gasket...a common problem you may encounter is a stuck head bolt...so if you are waiting for tools and materials...see if you can turn those bolts...don't force them if they don't want to turn...they break easier than you would think....start applying any penetrant that you prefer ...I like ATF mixed 50/50 with acetone....some guys like liquid wrench, kroil, PB Blaster...there are a few different ones...keep putting it on every day...a few times a day ...and bang on the bolts with a hammer.....hard...but not really hard...every time you put the liquid on...have a torch ready if you need heat
 

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@MARK (LI)
How does that ATF/acetone mixture compare to PB Blaster or other commercially available penetrants? I've heard of this before but never inquired further. Does it penetrate better or work faster or ?
 

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I like it....but that is why I said to use the one that you prefer...it seems there are a lot of opnions on what works best
 

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Yeah I like Boeshield for preventing corrosion and PB for breaking stuff loose that is already corroded. Guess I'll have to make up a small batch and try it out sometime! (y)
 
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