Lawn mower help

Hey guys,

My sister-in-law asked me if I wanted their old push mower(not too old self-propelled craftsman). They bought a new one as this one won't start. I figured what the heck I should be able to get it going. It is really clean looking, and would probably worth fixing and selling. Of course I can't get it running. The engine has compression, as I pulled the plug, and put my finger over the hole while having my son pull the rip cord. Sounded, and felt like plenty of compression. I used an inline spark plug tester, and it lit up, so I know it has spark as well. I pulled the air cleaner assembly off, and can look into the throat of the carb. I see fuel being pulled into the engine while starting. So it has all three things needed to run, but still won't. Any ideas? It is a Briggs and Stratton 180cc I think engine. I don't know much about small engines, but it seems like it has a really odd shaped throttle plate that is actuated by a linkage that is actuated by the fan on the motor. Also it appears to have a choke mechanism on it, but I have no idea how it gets pulled closed as I can't see where the linkage arm goes. When I pull the handle down on the handle bar it doesn't move any sort of linkage on the carb at all. How does it handle throttle aside from the linkage that is actuated by what looks like the fan? How does the choke work?On my push mower the choke is a manual/auto thing. You manually set it, and it automatically shuts off once the engine warms up. Any help is greatly appreciated.

Chris

You also need "spark and compression at the right time."

It is not uncommon for the key to shear in those, throwing the flywheel out of time. The ignition triggers off the flywheel.

How do I check that?

Dr. Hess wrote: You also need "spark and compression at the right time." It is not uncommon for the key to shear in those, throwing the flywheel out of time. The ignition triggers off the flywheel.

Big +1

All it takes is hitting something and the flywheel key will shear. BTDT, several times.

Mazdax605 wrote: How do I check that?

Pull the flywheel.

Hands down, I'd wager good money its a carb problem. I have probably fixed 200 of them working for Home Depot's repair department. Super simple. Pull the bowl off. Run a piece of wire up through the jet until you see it come out in the throat. blast some carb cleaner through the hole. Reassemble and it will start on the first pull.

As to operation of choke: The choke on these works very simply. There is a thermostatic coil that varies how far it closes based on temperature. Then the whole thing is connected to a plastic paddle that gets "blown" open once the flywheel starts blowing air. Therefore it is closed for pull starting and then opens once its running. The thermo coil prevents it from closing when its already hot.

Depending on the model, the bail handle could do one of many things. Usually it does two when let go; kills the spark and applies a brake to the flywheel. Follow where the cable goes. It typically ends with a spring attached to an arm.

I will second the possibility of a sheared crankshaft key. A good simple test that might help narrow things down... Take the air cleaner off (5/16" hex) and squirt one second's worth of carb cleaner in the throat. Give it a pull. If it starts for a few seconds, you need to clean the carb. If it doesn't start, chances are the timing is off due to a sheared key on the crank. Artificial fueling is a good way to determine if its not getting fuel, or not getting correct spark.

Find me the model number and serial number of the engine. It is either stamped on the tin above the muffler or stamped on the tin above the spark plug. That way I can look at diagrams of how your particular one should work. Model number of the mower wouldn't hurt either. That should be on the deck above the rear axle.

model number 917.370680

Toyman01 wrote:

Mazdax605 wrote: How do I check that?

Pull the flywheel.

Take the plastic and tins off the top of the engine. Take the nut off the crankshaft in the middle of the flywheel. Slide two long flathead screwdrivers or small pry bars under the flywheels and gently rock the flywheel back and forth. Don't pry hard or you'll break the flywheel or block. The point is to rock it back and forth until its free.

Looks like the bail handle actuates a mechanism for the bag, and maybe a brake on the flywheel, but nothing to do with the throttle.

Mazdax605 wrote: Looks like the bail handle actuates a mechanism for the bag, and maybe a brake on the flywheel, but nothing to do with the throttle.

Correct. The throttle is governed internally.

On my 917.380110 3.5 HP I found that the blade has to be in the proper position. An adapter is keyed to the crank and holds the blade in alignment. Weird , I know.

I sprayed some brake clean in the carb (didn't have carb cleaner) and it ran for a few seconds. I guess it is a carb issue.

Is the gas ok?

I had one of these and fought with the carb from new. After several tries at cleaning it and not having luck, I spent something like $30 on a new carb and it was good for a few years. Then I got a used Honda.

Start with the cheap stuff that tends to bite one in the ass. Throw a spark plug at it, check the flywheel key. If you are seeing fuel in the intake and not getting signs of life. I'd suspect ignition related. Usually it's a sheared key, make sure to replace with the correct aluminum one, it's a fuse.

EDIT: Didn't see the brake cleaner bit, that's usually pretty indicative of fuel. I'd still throw a plug at it though, I've seen them look/test fine and completely fail to function in an engine one too many times.

Gas in the cylinder is not the same as a clean, adjusted, working carb. All the spray-clean in the world isn't going to do the job. Pull it, clean it out with fine wire, then try. It's the only way.

curtis73 wrote: Hands down, I'd wager good money its a carb problem. I have probably fixed 200 of them working for Home Depot's repair department. Super simple. Pull the bowl off. Run a piece of wire up through the jet until you see it come out in the throat. blast some carb cleaner through the hole. Reassemble and it will start on the first pull. As to operation of choke: The choke on these works very simply. There is a thermostatic coil that varies how far it closes based on temperature. Then the whole thing is connected to a plastic paddle that gets "blown" open once the flywheel starts blowing air. Therefore it is closed for pull starting and then opens once its running. The thermo coil prevents it from closing when its already hot. Depending on the model, the bail handle could do one of many things. Usually it does two when let go; kills the spark and applies a brake to the flywheel. Follow where the cable goes. It typically ends with a spring attached to an arm. I will second the possibility of a sheared crankshaft key. A good simple test that might help narrow things down... Take the air cleaner off (5/16" hex) and squirt one second's worth of carb cleaner in the throat. Give it a pull. If it starts for a few seconds, you need to clean the carb. If it doesn't start, chances are the timing is off due to a sheared key on the crank. Artificial fueling is a good way to determine if its not getting fuel, or not getting correct spark. Find me the model number and serial number of the engine. It is either stamped on the tin above the muffler or stamped on the tin above the spark plug. That way I can look at diagrams of how your particular one should work. Model number of the mower wouldn't hurt either. That should be on the deck above the rear axle.

^^^ Nailed it. I have to fix my M.I.L. push mower every spring. It was stored with ethanol(gas with ethanol) in the tank, that crap absorbs so much moisture in one of those that has been sitting. It needs to be cleared out. Drain the tank, pull the plug, then pull the cord till you think your arm is going to fall off. Spray it out with starting fluid, and walk away. If you want to be really thorough pull the line between the tank and the carb. After it's sat for awhile hit it with the starting fluid again. Reassemble, pour some fresh gas in, preferably marine stuff if you can find it(no ethanol), with the filter removed give it a shot of starting fluid and a pull. Should fire right up, with a bungee or someone holding the lever to keep it running. Not engaging the drive, keep giving it a shot of starting fluid to keep it running. (don't be an idiot and keep a steady stream going, pulse it. Also, don't stand directly in front of the carb, stay off to the side) It should run on it's own in short order.

Pulled the carb, and cleaned it up(twice), and now the mower starts and runs really well. Well without the air cleaner on it that is. The filter is really badly clogged, and I will be getting a new one ASAP. What do you think a self propelled rear bagger mower is worth on CL? It is 5 years old by the way.

$100 maybe? That's a guess.

Without looking to see what others are asking, I'd ask $100, shoot for $70-$80 bottom dollar. Maybe add $20 to that if it's really clean and shined up.