I have a relative late model Craftsman rear-engine Briggs 13.5 engine, and have had trouble from the git-go.

The engine starts easily, and "sometimes" runs smoothly. However, about 50% of the time it "sputters", and misses a few licks -- black smoke comes out the muffler, and the thottle with "automatic choke" doesn't seem to change anything but speed. Occasionally, the motor smooths out, though (not rich), whether the blade is engaged or not.

I can't tell any difference from in the choke position or 1/2 throttle, except the engine shanges speed, so I presume

1) the choke is not functioning properly, either "floating" wherever it wants to and
2) the governor apparently works.

It has been back to Sears a couple of times, under warrantee, and the last time was out of warrantee, at a cost of about $300 -- still same problem. HELP!

Hi,
Sorry about your continuing troubles, and bill.
I would guess that it is not the choke, but I will attempt to tell you how to check it (machine and/or engine numbers would be helpful.) Put the throttle at idle and go to the engine on the side with the carb and throttle control. At the control mechanism there should be a link that operates the choke; it should have an open loop in it. I cannot say if it pushes or pulls as either is possible and I cannot look it up without numbers. Anyway, operate it and release it; a spring-loaded arm should pull it back when released. The arm should pivot a bit less than 90 degrees.
I am going to guess that the machine and engine operate just fine in a static environment. By that I mean, just running or possibly driven on paved surfaces. Your description is indicative of a fuel level that is too high in the float bowl. This could be caused by a less-than-ideal float and/or inlet needle. The reason I name both is that the float may not rise (float) in the way that it should, or the inlet needle may not seal as well as it should until the float puts extra pressure on it from a higher than normal level of fuel in the float bowl. There is another possibility, but it is exceedingly rare.
My solution probably would start by asking the repair shop (Sears, I gather) about their guarantee on their work, especially if it is within 90 days. Barring that I would replace both of the parts previously named. I can give part numbers if give engine numbers.
Peace,
Clarke

Hello, Crigby -- Thank you for your response.
The engine is a Briggs & Stratton 13.5hp I/C engine mounted in a Craftsman mower. There is a plate on the rear of the power with the numbers 5BSXS.3442VM and 276012. The motor has a plastic shroud on it which requires a Torx bit to remove. As you would expect, I do not currently have such. And, with the enclosed space, I was unable to find the spring loaded arm for the choke. I can remove some other ambiguosities, though. The mower, whether idling, full throttle, blade engaged, not engaged, machine moving or not moving (hydrostatic transmission) or any combination of such, the engine will run normally at times and at other times (more often) will run very rich. That is what led me to imagine a "floating" choke mechanism. I certainly hope it is not the carburator, although I understand your description of possibilities.
I hope this helps, and again, thanks.
-dj-

Hello, Crigby -- Thank you for your response.
The engine is a Briggs & Stratton 13.5hp I/C engine mounted in a Craftsman mower. There is a plate on the rear of the power with the numbers 5BSXS.3442VM and 276012. The motor has a plastic shroud on it which requires a Torx bit to remove. As you would expect, I do not currently have such. And, with the enclosed space, I was unable to find the spring loaded arm for the choke. I can remove some other ambiguosities, though. The mower, whether idling, full throttle, blade engaged, not engaged, machine moving or not moving (hydrostatic transmission) or any combination of such, the engine will run normally at times and at other times (more often) will run very rich. That is what led me to imagine a "floating" choke mechanism. I certainly hope it is not the carburator, although I understand your description of possibilities.
I hope this helps, and again, thanks.
-dj-

Hello, Crigby -- Thank you for your response.
The engine is a Briggs & Stratton 13.5hp I/C engine mounted in a Craftsman mower. There is a plate on the rear of the power with the numbers 5BSXS.3442VM and 276012. The motor has a plastic shroud on it which requires a Torx bit to remove. As you would expect, I do not currently have such. And, with the enclosed space, I was unable to find the spring loaded arm for the choke. I can remove some other ambiguosities, though. The mower, whether idling, full throttle, blade engaged, not engaged, machine moving or not moving (hydrostatic transmission) or any combination of such, the engine will run normally at times and at other times (more often) will run very rich. That is what led me to imagine a "floating" choke mechanism. I certainly hope it is not the carburator, although I understand your description of possibilities.
I hope this helps, and again, thanks.
-dj-

Hello, Crigby -- Thank you for your response.
The engine is a Briggs & Stratton 13.5hp I/C engine mounted in a Craftsman mower. There is a plate on the rear of the power with the numbers 5BSXS.3442VM and 276012. The motor has a plastic shroud on it which requires a Torx bit to remove. As you would expect, I do not currently have such. And, with the enclosed space, I was unable to find the spring loaded arm for the choke. I can remove some other ambiguosities, though. The mower, whether idling, full throttle, blade engaged, not engaged, machine moving or not moving (hydrostatic transmission) or any combination of such, the engine will run normally at times and at other times (more often) will run very rich. That is what led me to imagine a "floating" choke mechanism. I certainly hope it is not the carburator, although I understand your description of possibilities.
I hope this helps, and again, thanks.
-dj-

Hello, Crigby -- Thank you for your response.
The engine is a Briggs & Stratton 13.5hp I/C engine mounted in a Craftsman mower. There is a plate on the rear of the power with the numbers 5BSXS.3442VM and 276012. The motor has a plastic shroud on it which requires a Torx bit to remove. As you would expect, I do not currently have such. And, with the enclosed space, I was unable to find the spring loaded arm for the choke. I can remove some other ambiguosities, though. The mower, whether idling, full throttle, blade engaged, not engaged, machine moving or not moving (hydrostatic transmission) or any combination of such, the engine will run normally at times and at other times (more often) will run very rich. That is what led me to imagine a "floating" choke mechanism. I certainly hope it is not the carburator, although I understand your description of possibilities.
I hope this helps, and again, thanks.
-dj-

Hello, Crigby -- Thank you for your response.
The engine is a Briggs & Stratton 13.5hp I/C engine mounted in a Craftsman mower. There is a plate on the rear of the power with the numbers 5BSXS.3442VM and 276012. The motor has a plastic shroud on it which requires a Torx bit to remove. As you would expect, I do not currently have such. And, with the enclosed space, I was unable to find the spring loaded arm for the choke. I can remove some other ambiguosities, though. The mower, whether idling, full throttle, blade engaged, not engaged, machine moving or not moving (hydrostatic transmission) or any combination of such, the engine will run normally at times and at other times (more often) will run very rich. That is what led me to imagine a "floating" choke mechanism. I certainly hope it is not the carburator, although I understand your description of possibilities.
I hope this helps, and again, thanks.
-dj-

Sorry, people - I have no idea how the multiple postings happened. Please excuse me.
-dj-

Hi,
Sorry but those are the numbers off the EPA tag I believe. There should be a tag with model, type and code on it, should be black and silver, probably rivetted in place. Model probably begins with "28."
Incidentally, you usually get a chance to Edit for a short while after you post and think you can delete them; you may have to do it in Go Advanced.
Peace,
Clarke

Clarke,

You have been so kind to me, and I appreciate it. However -- I suspected there should be a rivited plate on the engine, so I removed the "cover" and looked all around -- can't find one.

Secondly, being somewhat familiar with small engines (and automobile engines, for that matter), I arrived at the original potential conclusion (fluctuating choke) based on my experience.

So, since I could not locate the model number plate (didn't look in the crankcase :) ), I took a photograph of the situation and have attached it as a .jpg file. To explain it a little (as if I need to), the carb has a governor controlled throttle, and the governor is "controlled" by the throttle cable (and spring and air). As far as I can tell, the governor is working fine, as is the throttle control. However, in the pic you will see the little black plastic (nylon?) lever on the top of the carburator that apparently operates the choke (yes, I can see inside the intake to see the choke plate, and suppose the throttle plate is after that), and there is absolutely no linkage to the choke lever -- no cable, no spring, nuthin' but air. I can flip the choke lever back and forth very easily, and I can see nothing that would engage or disengage the choke. If I knew where to hook what, I would be able to fix it, model number or not.

Ultimately, after the long winded discertation above, I believe there should be a tab, rod or something on the throttle cable linkage that would force the choke closed, and maybe a spring mounted to keep it open when it wasn't being closed, or something like that.

Can any of this help you help me resolve this issue?
Thanks.
-dj-

Hi,
Thanks for the photo! Have a number of graphics to give in return. It is indeed a Briggs since I can see their diamond emblem on the carb.
I do not see the choke pull off spring or the choke link in the picture. Guesses at each would be #691840 (link ref #216) and #690801 (spring ref #634) and those ref #s are the same for all Briggs engines. They seem to be missing.
I am posting three parts of your picture. One shows one of the nuts (7/16") that removes the air cleaner elbow; it needs to be removed. The choke plate will then be visible and may be removeable with nothing but a pair of pliers, if the screw is not present. Once the plate is out, the shaft will slip upwards and the spring installed (another picture shows the lever, top arrow for choke link, botton for the tab that holds the bottom tip of the spring - refer to carb picture.) Last of your snippets (those in color) is where the link goes - that slot in the control. My drawings are of the carb and the control plate with choke link.
To install it; do the choke first making sure that the spring is on correctly to open it automatically. BTW, do be sure to notice how the choke plate is on before so that you can make sure it looks like that afterwards! Remove the studs (5/16") holding the carb to the intake manifold, move carb away enough to hook small hook in end of link - it comes up from the bottom. Now slip carb in place at the same time you slip the long loop of the link into the slot (arrow on other picture) and fasten with studs. Put the air cleaner elbow and nuts back on. Reassemble the rest.
It really would be best to find some numbers somewhere so that I can verify the part numbers; no one except the factory will stock the new ones. You may find a dealer with a junk carb, however.
Peace,
Clarke

Clarke,

Thank you so much. You have given me more information than I ever expected.

This mower belongs to my neighbor (technically and mechanically challenged), and I will see if I can round up the two parts I need.

Ya know, your solution is just about what I envisioned. I have no idea why the mower was sold this way, nor why Sears couldn't fix it, or why the other shop couldn't fix it. When looking at it, it's obvious that it just ain't right. Oh, and the diagram you sent appears to be precisely the one for this engine.

Thanks again and stay tuned (no pun intended) for a success/failure report.

-dj-