John Deere JX75 Running Issues

 
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Old 07-11-2017, 09:06 PM   #21
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Re: John Deere JX75 Running Issues


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I don't see where it could be piston rings since the new plug made it run practically new for 2 cuts.
Well then another new spark plug will fix it up just right...for two cuttings

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When I pulled the starter cordt, the whole engine seemed locked tilting on its wheels as I pulled (just like weeks ago). It only loosened up to the point that I could pull the cord following quit a bit of romancing.
First focus on the motor locking problem. Then worry about fuel and spark, along with the engine actually running. What happens when you turn it over by hand? Can you see inside the cylinder? Do you have access to a bore scope to look inside? What is the compression reading? Is the oil metalic looking?
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Old 07-11-2017, 09:06 PM   #22
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Re: John Deere JX75 Running Issues


Until it got all clogged with oil deposits.
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Old 07-11-2017, 10:13 PM   #23
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Re: John Deere JX75 Running Issues


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Well then another new spark plug will fix it up just right...for two cuttings


First focus on the motor locking problem. Then worry about fuel and spark, along with the engine actually running. What happens when you turn it over by hand? Can you see inside the cylinder? Do you have access to a bore scope to look inside? What is the compression reading? Is the oil metalic looking?
Sometimes it started up without any resistance. Others, a mighty hard pull.

No bore scope unfortunately, or compression tester. But no metal in oil either. If there is gas in the oil it is not a lot, since its hard to tell.

I'm hoping the black plug is result of the float...

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Until it got all clogged with oil deposits.
Can the carb cause this?

The machine wasn't hydrolocked when the plug came out. Only does that on occasion.

Last edited by artinall; 07-11-2017 at 10:15 PM.
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Old 07-11-2017, 10:17 PM   #24
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Re: John Deere JX75 Running Issues


Might be running very rich.
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Old 07-11-2017, 10:36 PM   #25
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Re: John Deere JX75 Running Issues


So when I drain the Mechanic in a Bottle from carb bottom, should it changed from the "cleanout" if this might be the issue?
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Old 07-11-2017, 10:54 PM   #26
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Re: John Deere JX75 Running Issues


Thought he said just put fuel in the machine and run as normal.
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Old 07-11-2017, 11:12 PM   #27
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Re: John Deere JX75 Running Issues


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Checked oil - could not pick up on any gas there.

Plug is so dark it's hard to get a pic... this is the new plug with probably less than 2hrs ...
Clean it before putting it back in.
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Old 07-11-2017, 11:16 PM   #28
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Re: John Deere JX75 Running Issues


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So when I drain the Mechanic in a Bottle from carb bottom, should it changed from the "cleanout" if this might be the issue?
Who said drain, you just add the gas to the tank and go for it.

If it's something like a stuck float from gumming, it will clear up, at least some. If it's better but not quite there, you can always do it again.

If it's a corroded seat or a stuck float due to corrosion, it isn't going to clean up.

BTW, you didn't say if you cleaned the air filter (if needed). That can make it run rich, too.
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Old 07-12-2017, 12:02 AM   #29
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Re: John Deere JX75 Running Issues


According to the maker, they do drain it:

(the second example, start 5:47)

I understand the tiny hole of the carb jet can also clog.

Don't know if MIB can work on this too...

Last edited by artinall; 07-12-2017 at 12:14 AM.
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Old 07-12-2017, 02:17 AM   #30
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Re: John Deere JX75 Running Issues


If you are convinced it is the carb, why not take 20 minutes and tear it down to clean it?
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Old 07-12-2017, 07:59 AM   #31
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Re: John Deere JX75 Running Issues


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Originally Posted by artinall View Post
Sometimes it started up without any resistance. Others, a mighty hard pull.

No bore scope unfortunately, or compression tester. But no metal in oil either. If there is gas in the oil it is not a lot, since its hard to tell.

I'm hoping the black plug is result of the float...



Can the carb cause this?

The machine wasn't hydrolocked when the plug came out. Only does that on occasion.

The hard pull could be related to the flywheel brake shut off. Sometimes they stick

Edited to add that I'd go through the carb, too.

Last edited by rustyjames; 07-12-2017 at 08:20 AM. Reason: Additional info.
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Old 07-12-2017, 08:54 AM   #32
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Re: John Deere JX75 Running Issues


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The hard pull could be related to the flywheel brake shut off. Sometimes they stick

Edited to add that I'd go through the carb, too.
Any way to improve flywheel brake shut off?

May have to do carb, but linkage is a little weird on this one from what I remember... got one priced which I believe was not original, don't know if they are available but would want to find one.... the machine is 12 yrs + ... would rather keep instead of getting one of the newer ones.

If plug is that black, the cylinder might be a black hole.


Does MIB do anything for heavier carbon in cylinder? Probably cranked it a dozen times to get it to flow thru...

Last edited by artinall; 07-12-2017 at 08:58 AM.
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Old 07-12-2017, 10:12 AM   #33
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Re: John Deere JX75 Running Issues


MIB does nothing about cylinder carbon deposits. Those don't cause plug fouling.

RustyJames is right about the flywheel shutoff also being a likely cause of the hard pull. You can also hydrolock the engine by tipping it plug down - you'll get oil into the cylinder.
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Old 07-12-2017, 10:47 AM   #34
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Re: John Deere JX75 Running Issues


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MIB does nothing about cylinder carbon deposits. Those don't cause plug fouling.

RustyJames is right about the flywheel shutoff also being a likely cause of the hard pull. You can also hydrolock the engine by tipping it plug down - you'll get oil into the cylinder.
Perhaps the slope on our rear lot is doing this?
(only started this yr after moving to a steeper grade)

Anyhow -- drained, gased and fired it up.
Did find an arm off the top of the carb that was sticking it at rougher idle, severely, so cleaned it off with carb cleaner from outside. Freed it up somewhat. Goes through a smoother range of rpms ...

Runs better now but will see...

Last edited by artinall; 07-12-2017 at 11:25 AM.
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Old 07-12-2017, 11:14 AM   #35
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Re: John Deere JX75 Running Issues


If getting a new carb or rebuilding is expensive, too time consuming, whatever, cleaning is never wrong. There is still some useful cleaning and an easy check that can be done.

-Air filter clean or replacement, if you haven't already.
-Gas cap clean. The vents can get blocked and cause problems, but usually that's noticed when it starts running lean after using it for a time. You could also run with it loose, so it can't pressurize or pull a vacuum, but that tends to get gas everywhere if you do it with a full tank.
-Clean the outside of the carburetor. I mostly use non-flammable spray cleaner for this. You'll want to do this if you get into the carb at all any way.
-Try to find the bowl vent and give it a spritz of carb cleaner- it's an air passage that goes from the bowl to outside air, but the location varies from carb to carb. Sometimes the easiest thing to do is remove the bowl and find the vent, then clean it from the bowl side, it's just inconvenient doing this with a mirror. I'm on the fence on this one, since this is usually better done as part of a carb rebuild and you have to replace the bowl seal before reassembling, but I have done it.

Keep in mind, this is all based on the plug fowling, so it seems to be running rich. There are other possibilities, but they aren't as likely.
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Old 07-12-2017, 11:26 AM   #36
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Re: John Deere JX75 Running Issues


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Originally Posted by artinall View Post
Perhaps the slope on our rear lot is doing this?

Anyhow -- drained, gased and fired it up.
Did find an arm off the top of the carb that was sticking it at rougher idle, severely, so cleaned it off with carb cleaner from outside. Freed it up somewhat. Goes through a smoother range of rpms ...

Runs better now but will see...

Cleaning is never wrong!

Normally mowing a slope shouldn't cause you a problem, even if you run it half the time with the plug down slope. It would only show up as a little more oil usage, and you should be watching that even on a new engine.

With the engine off, yes, you can get enough oil accumulating in the cylinder on a steep slope to cause hydrolock, and you'd just have to wait for it to drain back out. I don't think this is your problem for the hard pull issue.
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Old 07-12-2017, 02:18 PM   #37
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Re: John Deere JX75 Running Issues


Most likely gas is going into crankcase, raising oil level, & then hydrolocking. The very black plug is the give away that the float isn't shutting the fuel down. If left to sit long enough, the oil will absorb the gas, just like in a 2 stroke mix. Then it just ends up looking like too high of an oil level.
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Old 07-12-2017, 03:34 PM   #38
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Re: John Deere JX75 Running Issues


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Most likely gas is going into crankcase, raising oil level, & then hydrolocking.
I think he said he smelled the oil and didn't smell anything, but it could have cooked off.
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Old 07-12-2017, 03:49 PM   #39
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Re: John Deere JX75 Running Issues


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I think he said he smelled the oil and didn't smell anything, but it could have cooked off.
yes, small trace if anything...

Would straight 30 weight over 5-30 help?
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Old 07-12-2017, 03:49 PM   #40
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Re: John Deere JX75 Running Issues


If the float was sticking it simply wouldn't run, period. Way to much fuel would be flowing in to run it, let alone start it. Most likely the fuel tank would be found empty.

Again in about 20 minutes you can remove the carb, take it apart, clean and blow the passages and jets out, put it back together, and reinstall it.

FWIW I have never seen a small lawn mower with a flywheel brake, but I am not a small engine technician, as there is no money in fixing them. Usually the engine just has an electrical kill switch. Timing at the flywheel could be off though, and if it is variable it could be sticking.

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