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Small Air Cooled Gasoline Engines Briggs & Stratton, Clinton, Lauson, Maytag, Nelson, Wisconsin and other small air cooled engines.

Small Air Cooled Gasoline Engines

Briggs and Stratton 5hp


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  #1  
Old 01-16-2012, 11:40 AM
lihelp lihelp is offline
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Smile Briggs and Stratton 5hp

I have an old atlas showblower with a 5hp Briggs and Stratton engine. The engine is at least 20 years old. I use it every winter and always start it up in the summer and late fall.I tried to start it last week and it would not start. It has an electric starter and that was working. I pulled the plug and than attached to the wire . I used the starter and was not getting a spark from the plug. What is the next step to take?
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Old 01-16-2012, 02:08 PM
sprkplug sprkplug is offline
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Default Re: Briggs and Stratton 5hp

Disconnect the kill switch and any safety switches that might be present, and retest spark. If you still don't have any, then I would suspect a problem with the points, if it is so equipped. If it is electronic ignition, unhook the kill wire at the coil/armature and retest spark. If you have spark then, it is most likely a switch you forgot to unhook, or a short in the kill wire itself. If there is still no spark on an electronic ignition unit with the kill wire unhooked, then you're looking at a new coil/armature.
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Old 01-16-2012, 02:14 PM
Andrew Mackey Andrew Mackey is offline
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Exclamation Re: Briggs and Stratton 5hp

On any engine, check all shut off switches, controls, and safety devices, to make sure they aren't shorted or damaged. On the 5 HP, I have seen many failures, over time, of the plastic block that holds the mag kill wire and the shut off switch combo. The plastic degrades, allowing the switch to short out. Check the spark plug itself. If it gets wet with fuel, it will short out under compression, and if there is carbon on the insulater, in the combustion side, it will not fire either. After checking all of these, you still have no spark, then check the following:

The answer lies between 2 places - does your engine have points or not. If there are wires leading under the flywheel, from the mag coil, then the probability is the following: The most common problem with the older 5 HP B&S is the fact that combustion and crankcase gasses get into the timing cover, and the condensate from these products condense on the points! This, of course, oxidises the points, so no spark.

To remedy, you have to remove the starter cover/shroud, remove the flywheel fan screen off the starter pawl assembly (if your engine has a screen). Re-install the screen mounting screws and then remove the starter pawl assembly (turns counterclockwise). You can either get a tool especially made for this job , or use a piece of brass or aluminum and a hammer (crude but will work). Next you have to remove the flywheel. This might entail the help from a friend. You have to pry the flywheel away from the block. Place a piece pf brass or aluminum against the end of the crankshaft, hit it sharply with a fairly good sized hammer. This should shock the flywheel loose of the crank. Note: DO NOT HIT THE END OF THE CRANK, DIRECTLY WITH THE HAMMER If you do, you will mushroom and distort the soft crank metal,,and the starter pawl will no longer fit on the crank (BOO-HISS). DO NOT hit the flywheel either! You might bend the crank, or crack the flywheel hub! Once the flywheel is loose, remove it from the engine, making sure you do not loose the key. The ley will be a bit of aluminum, anout 3/32" wide, 1/8" theck and about 1/2" long. It should be in perfect condition, with no offset or shear indications in the sides. Once the flywheel is off the engine, you should see an aluminum cover, held with 2 - 1/4" headed bolts. Remove these bolts and then remove the cover. This will expose the points. Clean the faces of the points with a fingernail sanding board, placing between the points and drawing it out until nearly off the faces. Repeat several times. Close the points and place a white business card between the points. Pull out on the card, but do not pull clear out of the points. Repeat until the card comes out clean, with no grey deposit on the card surface. On the last cleaning, open the points by turning the crank, and set points at .020". Place the flywheel in place, and install the flywheel key. Gently spin on the starter pawl, to keep the flywheel in place. Remove the spark plug, and ground it to a clean metal spot on the engine. Spin the flywheel in the normal direction of rotation, now you should have spark. If you do, remove flywheel and key, and re-assemble the engine, with the exception of the shroud. If no spark, chances are that the condenser has gone bad. Rarely have I found a bad coil, on a points fired 5 HP. Make sure that the starter pawl is good and tight. If it is loose, the flywheel key will shear off! One last thing to do: Place a post card between the flywheel and the mag, and turn the crank until the magnets are directly under the magneto. Lift up on the starter pawl assembly, and try to slip out the post card. If it is stuck, all is well. If you can pull it out easily, replace it in position, with the magnets under the mag, and loosen the mag mount bolts. Let the magnets pull down the mag, until it rests on the card and the magnets. Again, pull up on the starter pawl, and then tighten the mag mount bolts. Remove the card, and all is good.

If the engine is of the ponts less ignition system, the mag itself may be suspect. Double check the mag to flywheel clearances, as outlined above, and re-set if nescessary. Using a clean new spark plug, test for spark. Make sure that the starter is turning the engine at at least 700 RPM, or you might not have spark. Make sure that the high tension wire is not pinched or cut by the engine shroud, and make sure there are no cracks in the insulation surface.

Andrew
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Old 01-16-2012, 02:21 PM
1916Z3 1916Z3 is offline
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Default Re: Briggs and Stratton 5hp

Most likely cleaning the points will take care of the problem. I am at this point just assuming what engine you have.

Cleaning the points procedure would entail taking the heat shield around carb and recoil/starter/windshroud housing off, removing flywheel and then using a 1/4" socket removing the point/condensor cover that will be revealed by removing the flywheel. you should then see the point set and whatever is on the contacts that is causing the no-spark problem. Usually it's moisture and rust. take a small piece of fine sandpaper and fold it in half (grit side out) in which it will sand both contacts at the same time. after sanding the points and you are confident you have removed the corrosion I usually take some contact (electrical cleaner) and sparingly spray the contacts off and then also you can use a T-shirt type material and drag through the points to be sure they are clean. Also, you will want to check the point gap. turning the crankshaft a couple revolutions at this time is also a good idea to observe the points opening and closing as sometimes the plunger piece that opens and closes them can get stuck and not allow the points to close. to adjust the point gap you move the condensor farther or closer to the movable point. to do that you use the 1/4" socket again and loosen the hold down clamp on the condensor a tiny bit just so you are able to move the condensor and at that point make sure the points are in the opened position of timing and set the gap at 20 thousandths and lock down the condensor clamp bolt again observing that the condensor didn't move while you were tightening the bolt. at this point reassemble engine to the point of flywheel being back on the crankshaft and tightened. you can then at this point being careful to not have anything in the path of the flywheel give the engine a quick spin with the electric start to observe if you now have a nice blue spark. If you do have a nice snappy blue spark, reassemble engine the rest of the way and it should now run.

---------- Post added at 12:21 PM ---------- Previous post was at 12:16 PM ----------

ok.. I guess I took to long to type this out and ended up with 2 replies before mine.. sorry if I said something that has already been said.. or missed something that should have been said.. haha

Andrew Mackey is a pro at these posts so I am sure his will make more sense and be more thorough
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Old 01-16-2012, 02:43 PM
qt442w30 qt442w30 is offline
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Default Re: Briggs and Stratton 5hp

Just a thought but I have a older Powermate 5K Generator that I picked up in a dump site (That is free) that someone threw out, about 20 years old now. It had no spark but otherwise looked very nice and functional, with a 10HP briggs. After studying the ignition system, I learned it had a low oil sensor in the crankcase that under normal conditions is an open circuit to the ignition. When the oil drops below a given low but still safe level, it applies a low resistance short to the ignition coil, just enough to kill spark but not damage the ignition circuit. I then looked at the oil level and indeed it was low. Added a little oil and the short was gone. That was all it was but one would have to know where to look. The guy that threw it out had no idea it just needed a little oil as it still showed a safe level....
Just a thought. Not sure if snowblowers were sold with similiar safety system. Gens are normally left unattended...
Good luck.
Dave
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Old 01-16-2012, 03:50 PM
lihelp lihelp is offline
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Default Re: Briggs and Stratton 5hp

thank you for all your help. I checked the oil and that was full. The next item I checked was the key lock which prevents the snow thrower from starting. I pulled it out and put it back in to make sure it was making good contact. It started right away.
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Old 01-28-2012, 08:07 PM
Andrew Mackey Andrew Mackey is offline
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Exclamation Re: Briggs and Stratton 5hp

Sometimes it's the simple things. Glad you found the problem before tearing things apart. Sometimes safty devices can drive you nuts, I can tell you from experiance. I didn't know your machine had that item, or I would have told you to check them first. Many Sno King Techumseh engines have a pull key kill switch. If salt gets on the switch, spark can come and go, driving you crazy trying to sort out mag problems. On these snow blowers, the first thing I do is pull the key in and out several times. 70% of the time, the simple action will revive spark.25% of the time, the plastic has degraded and shorts out the mag, and the last 5% will make you pull your hair out (mice, dirt, bad coil, broken wires, you name it)

Good luck with your machine, and don't for get to keep fresh gas in it!
Andrew
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