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I have a JD mower with a FS730V that has an intermittent smoking issue. The motor has 313 hours and it works great minus the thick white/blue smoke it generates ever so often. I did a compression test and came up with 90 on cylinder one and 92 on cylinder two. It also appears that I may have some gas in the oil. I’ve recently changed the plugs and oil but the smoking seems to be unchanged. I’ve ordered a new fuel pump but was curious if anyone has any other suggestions. The motor seems to bog down right before it begins to smoke but the smoke stops after several seconds.

Shadytree said:

It also appears that I may have some gas in the oil.

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I would correct this first. After corrected dump the oil and filter a couple times.

Also you must park the oil dip stick on TOP OF THE THREADS when checking the level. Do NOT screw all the way down into the tube like on a Briggs for example.

slomo said:

I would correct this first. After corrected dump the oil and filter a couple times.

Also you must park the oil dip stick on TOP OF THE THREADS when checking the level. Do NOT screw all the way down into the tube like on a Briggs for example.

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Thanks, I’m guessing either the fuel pump diaphragm is allowing fuel back through the pulse hose or my float in the carb is stuck? If the carb float is stuck would that result in poor engine performance?

Shadytree said:

Thanks, I’m guessing either the fuel pump diaphragm is allowing fuel back through the pulse hose or my float in the carb is stuck? If the carb float is stuck would that result in poor engine performance?

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I pulled the crankcase breather hose from the carb and it was full of oil. I crafted a catch can after draining the oil and replacing it and drove it around for 30 minutes or so. It didn’t smoke but the catch can had a solid quart of oil in it. Does this mean the rings are shot or could it be the breather reed valve?

Shadytree said:

I pulled the crankcase breather hose from the carb and it was full of oil. I crafted a catch can after draining the oil and replacing it and drove it around for 30 minutes or so. It didn’t smoke but the catch can had a solid quart of oil in it. Does this mean the rings are shot or could it be the breather reed valve?

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With that amount of blow by, most likely rings need to be replaced at a minimum . Had this on a customer’s Honda two years ago. Take breather tube off of carburetor and it was shooting a mist of oil. Replaced rings, and hand scoured pistons with green Scotchbrite pads (slight vertical scoring). It was also smoking like a freight train before the repair and using oil like crazy.

How about the carb needle and seat?

Tiger Small Engine said:

With that amount of blow by, most likely rings need to be replaced at a minimum . Had this on a customer’s Honda two years ago. Take breather tube off of carburetor and it was shooting a mist of oil. Replaced rings, and hand scoured pistons with green Scotchbrite pads (slight vertical scoring). It was also smoking like a freight train before the repair and using oil like crazy.

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Going to take it apart to see the damage….

Shadytree said:

If the carb float is stuck would that result in poor engine performance?

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Fo sho

Leak down test showed my rings are shot, also found metal in the oil. Replacing with new engine. Can’t believe this engine failed with only 313 hours…

Are you bagging ?
The FS series have very poor designed air filters and if over tightened will allow unfiltered air to enter the engine .
This is a problem with a normally used mower but with a ZTR with bagger it is a disaster
I have re-ringed 3 to date and all of them were on TimeMasters with baggers fitted .
Good news is all they needed was a light hone & new rings so pull yours down first before deciding on replacement .

Shadytree said:

Leak down test showed my rings are shot, also found metal in the oil. Replacing with new engine. Can’t believe this engine failed with only 313 hours…

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Hope you did this test at TDC right? Didn't leave a valve open?