Craftsman 18.5hp engine issues - Model 917.273811


Old 08-31-06, 09:54 AM
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Craftsman 18.5hp engine issues - Model 917.273811

Hello all, I need some ideas here. I've got a 3yr old Craftsman 18.5hp, 42" deck mower with a briggs & stratton single cylinder engine on it. Suddenly I'm losing power and the engine's running at top end, I can't even throttle it down. Only way I can throttle it down is to move it into a choke position at the top. Last time I mowed it seemed to run ok (2 wks ago), but last night I could barely get it up our slightly inclined yard, but it would run better heading downhill. First I thought it was low on gas, filled the tank, no change. Then I checked the oil, fine there, then pulled the engine shroud, checked to make sure the fins weren't clogged (they weren't), pulled the fuel line, it seemed to flow ok, (I'm not sure how much fuel should be running thru it via gravity).

It starts & runs fine, just at wide open throttle now, even when I have the throttle down to the "turtle" speed. Plug is a bit on the black side but nice white tip, seems to be running rich now at full bore.. I can't figure this out. I'm planning to replace the fuel filter and even the drive belt, I'm wondering if its slipping. But I don't know what to do about the fast running & inability to throttle the engine down. The throttle cable seems fine, it lines up with the "A" holes in the Governor plate as the manual says it should... I've read a few other responses in here about possible vapor lock, I didn't think to check the fuel cap, will tonight, the other thing bothering me is the fact that the fuel line runs next to the engine on a bracket if you will, I saw something about overheating which in a way makes sense because its running so fast. Damn thing is only 3yrs old, help????
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Old 09-01-06, 12:52 AM
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Is it racing (over-speeding) or just running at full governed throttle?
Old 09-01-06, 01:28 AM
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I have several of these engines but I've never experienced this problem. Point is someone else will respond with a more concise and more direct answer but let me throw out a few ideas. My first question would be "Are you sure the throttle linkage is indeed working properly"? When you move the throttle can you see the throttle arm on the carburetor move? The 18 hp engines linkage allows the throttle arm to move with little regard for the governor? The throttle is however, linked closely with the governor and can be forced to full throttle if there is a linkage or governor problem. Can you move the governor arm on the engine itself up and down and feel a slight resistance? If NOT you could have a governor problem! If YES then you probably have a broken cable or linkage problem? If the throttle arm on the carburetor is responding FULLY from the extreame low end to the extreame high end when you move the throttle then your problem must be within the carberator. Someone with more experience than me will have to describe what internal carberator part could fail or become restricted to cause this problem since I've not seen it. The only logical possibility I can conceive is that the throttle plate on some models are screwed on and has come loose. While I've never seen one come loose, I guess it is possible. The other type throttle plate you slide into an opening along the throttle rod. I can't see how it would be able to come completely out, I guess it could. If it simply slipped from it's proper position then I think you would have been unable to move the throttle arm properly to begin with? IF the govenor and linkage is all working properly then to resolve this problem I would remove the carb and if I didn't find an obvious reason for the problem I would simply soak the carb in a carb bath overnight, clean it up with carb cleaner from a spray can, blow all the openings carefully with compressed air and rebuild it. Maybe this ditride will at least give you some idea of a few things that could be at fault while we wait for a pro to chime in? Good luck, Ron
Old 09-01-06, 06:52 AM
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I have seen a few internal carb issues dealing with the throttle plate/valve. Usually two small screws hold the plate to the shaft. I've seen the screws come out and the plate wedge in the throat, I have seen the shaft break though one of the screw holes thus wedging the throttle plate.
If it is running faster than normal (racing) and the linkages seems to move the throttle shaft, I would certainly check to see that the throttle plate is still working and in tact. If it wedges in the throat, usually it will be stuck beyond where it would normally open, which can cause it to overspeed. Since it is not meant to run this speed the carb may not be able to supply enough fuel and cause it to run lean. Some indication of lean condition would be white on the spark plug. Since the carb cannnot supply the engine with enough fuel, when under a load it may loose power and even die.
The black on the plug could be from running it with the choke. If you do have an overspeed and lean condition, you should not run the engine until the problem is found and corrected.
Old 09-01-06, 08:26 AM
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18.5hp Briggs Engine Issues --

Wow, thanks guys you all had ideas I hadn't thought of, I'll have to check all of this over the weekend since I didn't have time last night.... (Besides my lawn looks good as a hayfield :>)

Good points, much appreciated I'll be back w/answers soon....

Old 10-09-06, 10:30 AM
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Craftsman 18.5 Engine issues update - It was da' Guvna...

It took me awhile to get back to this one, too much on my plate... For those who were interested, it turned out to be the Governor... I finally broke down & had a Sears tech come out to look at it. To a 3rd person it would have been almost satirical to watch, he started it up, ran it no more than 10 seconds, then shut it off, turned around and said to me, "Governor's bad, you need a new engine".... What, whoa... hold on a minute, what'd you just say pal??? I sort of had that "O" face, like what just happened here....

He explained that it was the governor, but that the labor involved to replace it exceeded the cost of just replacing the entire engine...He said it wasn't a customer/owner fault issue, completely an internal mechanical failure.. As the result, the replacement was warranteed, full replacement, no cost to me...

So... a week went by, had a new B&S motor sitting in my driveway one day, he came 2days later & did it... Took 2 passes at my lawn to get it cut fully, but things are back to normal...runs great, again...

My only comment on this whole thing is... 2 years/seasons of non-commercial mowing, and something major like this happens? Tractors & engines used to last 10-20yrs, or more... Our first Craftsman in 80/81 was used hard on a 6acre farm for 12yrs and was still running like a champ when we sold it with the house...That one had a Briggs engine in it too... Whatever happened to the quality you should expect from companies like B&S.. sad really...

Guess I'll have to sell it at the beginning of 2008, before it blows again....
Old 10-09-06, 12:12 PM
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Cool Bad Governor

Well that is not a common problem, although it does happen. I really wonder if the governor failed, or if it was something else. I have seen technicians jump to conclusions before, however since it was covered by your service agreement, all worked out ok.

I don't think you have to worry about this being a common problem and I would think it unlikely to happen again. I was more inclined to agree with another poster about the screws comming out of the throttle plate in the carburetor. That is much more common occurance than the governor failing.
Old 10-09-06, 12:14 PM
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Thx for getting back with the info.
10 seconds aye, govenor aye, LOL
thats one helluva tech...
Maybe if there was a service bulletin of some sort on that engine but Puey could check that...
Bottom line is you got it goin and a new engine to boot

Unfortunate truth is its actually cheaper for companies to take a chance on less quality in parts and assembly than it is to replace the few that actually make it back for warranty replacement.

Glad your all fixed tho
Old 10-10-06, 06:26 AM
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Location: Upstate New York
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Having been in the business over 25 years, I'd say you got one hell of a deal for which you can thank Sears. Or, maybe the technician. Briggs would never replace the whole engine if it were simply a governor issue. I'm sure it was, in fact, an internal governor issue, but it doesn't appear the tech performed a thorough diagnosis although he likely got the end result correct. Briggs, as well as I, being a business owner, would demand that the engine be disassembled and inspected before a replacement engine be authorized. As far as need in worrying about future trouble, I don't think so. As far as inferior parts, no. It's just one of those things that can fail. As far as the throttle plate screw(s) go, I've seen far fewer of these back out than governor gears/spools go bad. Note that I could not find the model number you posted in parts lookup on the Sears site and you also provided no engine numbers for us to reference. In the future, if you have engine trouble, please provide the engine ID numbers as well.
Old 10-13-07, 01:18 PM
Join Date: Oct 2007
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Bad governor on mine too

I had the exact same symtoms with mine then it blew a rod on top of that. I replaced the rod and it still raced so I called Sears, the guy came out and declared it dead with a bad governor. Sears replaced the engine for free. It was still under warranty by 2 weeks.

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