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Question DetailsAsked on 12/21/2017

my JD 345 occaisonly spews a cloud of smoke from exhaust. 18 hp liquid cooled Kawasaki.

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1 Answer


Common causes of this:

1) water in gas, causing plug misfires as the water gets pulled through the intake screen or inline filter in globs - can also cause gas float (if there is one) to misbehave, causing intermittent flooding as it runs.

2) blocked air filter causing it to run over-rich - normally would run and then gradually taper off in rpm's/power like it was going to die completely, but then before dying surge back to full or near full power, putting out the slug of smoke at that time (excess fuel being burned). Usually does this on a fairly regular interval if under steady load, as it transitions from proper to overly rich mixture as it starves for air, then back to normal as the rpm/s drop off enough that it is again getting enough air for that engine speed/power.

3) plug wires or coil wire failing, loose, or shorting out - causing intermittent electrical failure at plugs, so engine falters and is not burning the gas coming in at that moment, then when it kicks back in it shoves out the excess gas plus burns what is in the exhaust system, causing a puff of smoke (and maybe explosion in the exhaust system).

4) brake on - either blade or wheels, so the engine is lugging down and building up unburned fuel due to engine being loaded down too much (much like a diesel lugging down on a hill and cranking out excess smoke)

5) engine lugging down because the throttle setting is too low, so rpm's are not high enough for the work it is being asked to do

6) automatic or manual choke linkage loose so it is running rich

7) governor vane jammed or loose linkage so it is being rpm controlled intermittently, causing engine cutback at that time even though under load still so it is still turning and pulling fuel in, then when it starts firing again burns that excess fuel. (Some governors intermittently cut the spark untill below governed speed like described above, some directly regulate the throttle so that would not cause this though can cause surging).

8) rarely a head gasket going bad or a loose plug so it is intermittently losing compression enough that it is not firing off and on, shooting that unburned fuel out hence causing the cloud of smoke

9) rare but happens - seat safety switch 9which cuts out the power if you are not sitting in the seat) is out of adjustment so as you bounde along it is cutting in and out, causing unburned fuel surge of smoke when the power cuts back on again

10) the lawn gnome powering it in the treadmill has taken up cigar smoking

Note excess gas smoke will generally be black or gray, oil smoke blue or bluish-gray, white means coolant leaking into the combustion or exhaust system.

If this did not help, the professional Search the List category for find well-rated and reviewed vendors to work on it is Lawnmower and Power Tool Repair.

Answered 2 years ago by LCD

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