LT1000 Running Rough

JMetzMay 2, 2014

Hi all,

I inherited an older Craftsman LT1000 when I bought my house a few years ago. I've been changing the oil & filter, fuel filter, air filter, spark plugs regularly and it's been running great. Did the same thing this year.

Had it up and running fine last weekend. There's a notch in the throttle that says "Throttle here for mowing" (or something similar) and I had it set there while mowing. I inexplicably raised the throttle past that point while mowing. I immediately realized what I did, but the engine start sputtering and died before I could get the throttle back down.

I tried to restart the mower but it wouldn't start, so, I let it sit for a while and then got it running. When it started, it was spitting out a lot of grey/white smoke, so I let it run and run. As it ran, however, it was louder than normal, with the occasional "pop". I pulled the spark plug, which was new, and saw that the tip was black and covered with soot. So, being that I had a spare spark plug, I replaced it. But when I started the mower back up again it's still running loud with that "popping" sound.

Also, I should mention that when I put it in gear it's moving slower than normal, and if I engage the blades, I can hear that they're not moving at normal speed.

Any advice would be much appreciated. I can't easily get this into a repair shop, so anything I could do on my own would be great.


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You should provide model numbers for the tractor and the motor so we know what we are dealing with. LT1000 covers quite a few to guess at.

What you did was choke it to death when you first raised the throttle lever and since it seems to be exhibiting the same symptoms I would look under there and see if you can see the choke working or not. Perhaps the choke butterfly in the carb is stuck closed or partially closed.

    Bookmark   May 2, 2014 at 9:06AM
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Sorry, I overlooked including the model numbers.

Tractor: 917.275391
Engine: Briggs Model No. 31H777-0297-E1

    Bookmark   May 2, 2014 at 9:29AM
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Agree that the choke butterfly may be stuck shut.
Remove the air cleaner to check.

If you don't have an Owners Manual, click the link.

Here is a link that might be useful: Owners Manual

    Bookmark   May 2, 2014 at 9:54AM
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Thanks for the advice. So, if I just remove the air cleaner and likely the housing cover, I'll be able to see from there if the butterfly is stuck? If so, would I need to remove the carburetor and clean it all out, or is it something I can do with the carb still attached?

(Based on the amount of upkeep the previous owner did on the house, I imagine he didn't do much on the mower either. It would probably be best to clean the carb out anyway, but for the sake of getting the mower back up and running to cut the lawn this weekend, I'll wait on that until I have more time.)


    Bookmark   May 2, 2014 at 10:08AM
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If the mower was running well before this happened, it's not a "given" that the carburetor needs cleaning.
But seeing as this machine is circa 2005, a good carb cleaning certainly might not be a bad idea.
It is also important to determine whether the control cable is still secured at the correct position by its anchor clamp.
If the cable outer housing/sheath has moved under its hold down clamp, the "mowing position" setting indicated on the control panel will not place the actual carburetor into proper corresponding position. That scenario could mean that even though your control panel setting indicates the "mowing position", the carb itself may be in "choke mode".
And even if you do decide to do a carb cleaning, the control cable anchor clamp needs to be checked for proper operation and cable adjustment after installing the carb.

Another thought on the situation is that what you are now experiencing is due to the cylinder head gasket having failed completely.

This post was edited by mownie on Fri, May 2, 14 at 11:19

    Bookmark   May 2, 2014 at 11:13AM
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Assuming this isn't a failure of the cylinder head, what's the best process for troubleshooting?

First, check the throttle control cable to make sure the holes are aligned. If so, or after alignment, try the mower. If problem persists, then check choke butterfly?


    Bookmark   May 2, 2014 at 11:43AM
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That's pretty much what you need to do.
If you find the choke to be closed or partially closed, you may want to temporarily "tie" it open with a wire to make sure the engine will perform properly (good power and no smoke).

    Bookmark   May 2, 2014 at 11:51AM
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If it turns out that it is the butterfly choke that's causing the issue, can I use a carb cleaner with the carb still fully assembled, or will I have to take it apart in order to clean it and get it moving again?

    Bookmark   May 2, 2014 at 12:17PM
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IF...the choke is failing to return to the open position due to a "sticky" condition, it will be OK to clean the choke shaft pivots with the carb intact, and still on the engine.
But I would make certain to use adequate "shop towels" or rags to protect nearby surfaces from spatter or overspray. Protect your eyes too.
Also, I have read some posts in threads where forum members installed a light duty return spring into the choke linkage configuration to ASSURE that the choke butterfly is held open, except when the control cable draws the choke closed.
I can't recall exactly which member(s) have done this but perhaps one of them will read this and chime in with how they accomplished their add on fix.

    Bookmark   May 2, 2014 at 12:52PM
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Excellent. I feel better knowing I've got somewhere to start in my troubleshooting. I plan on looking into this tomorrow, so I'll check back with any updates.

Thanks to all for the advice/information.


    Bookmark   May 2, 2014 at 1:11PM
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