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Small Air Cooled Gasoline Engines

Briggs & Stratton 5S Engine No Spark


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  #1  
Old 12-19-2008, 03:38:38 PM
whargrov whargrov is offline
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Default Briggs & Stratton 5S Engine No Spark

I have a Briggs and Stratton 5S that my father rescued back in the early 60's and was used to pump water at our camp for years. According to the serial number is was manufactured in 1951. Has not been run in 20 years and I am attempting to get it going again. Got it turning, cleaned out the gas and air intake. Everything seems fine except I do not get a spark on the plug. I am not familiar with points and condensers. It generates voltage when I try to start it, voltmeter measured 100V or less. Enough to shock your hand (I found out) but evidently not enough to spark the plug. Any advice that will get me a spark will be appreciated.
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Old 12-19-2008, 04:43:19 PM
CJBennett CJBennett is offline
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Default Re: Briggs & Stratton 5S Engine No Spark

Your going to have to remove the flywheel. Behind that you'll see an aluminum cover held on by 2 screws. Remove that. Next thing you want to do is file (with a nail file)or use emery cloth where the points contact each other. They should be set at a tight .020. Make sure everything is clean and reassemble. You should have spark now, if not replace condenser.
CJ
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Old 12-19-2008, 05:08:55 PM
K D Redd K D Redd is offline
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Default Re: Briggs & Stratton 5S Engine No Spark

I save a 5S sold by Sear which turned out to my Birthday engine, 8/1950 from a junk man. all I had to do was clean the point and she had fire. I also had to clean the crankcase, fuel system and reseat the valves. She runs like a top now.

Kent
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Old 12-20-2008, 09:45:23 PM
whargrov whargrov is offline
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Default Re: Briggs & Stratton 5S Engine No Spark

Tried cleaning the points but still no spark. I was very relieved when the flywheel came off very easily. Will try replacing the condenser. Attached is a picture of the engine.

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  #5  
Old 12-20-2008, 11:25:37 PM
KirkWallace KirkWallace is offline
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Default Re: Briggs & Stratton 5S Engine No Spark

The other thing I have seen mentioned on this forum is the magnet in the flywheel can lose its magnetism. I suspect this doesn't happen very often. Is there a simple, reliable method for checking this? I just use a wrench to see how much force is needed to break free from the magnet, but this isn't very sophisticated.

For the condenser, you can use a voltmeter to check for continuity between the terminal on the flying lead and the condenser housing. If you get continuity, then there is a short inside. There could be other condenser issues but continuity is easy to check. I suppose you could put 12 Volts on the condenser, disconnect the 12 Volts and measure the condenser voltage to see if it can hold a charge. This just came to mind, so I haven't tried this yet. The reason I mention the condenser, is that my engine with the absolute ugliest condenser has the strongest spark. I was hoping that it was bad, so I could replace it with a shiny new one, but it seems to work just fine.
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  #6  
Old 12-21-2008, 12:01:45 AM
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Default Re: Briggs & Stratton 5S Engine No Spark

Checking flywheel magnetism doesnt have to be sophisticated. It's really simple. As long as you have a good sharp grab on the screw driver by the magnet then thats all it needs to produce a hot enough spark to fire. If you have a weak grab by the magnet which means it sorta grabs the screw driver or what ever you chose to use and if you let go and the screw driver falls right off without effort then the magnets are no good and the flywheel needs replaced or magnets charged. It's not very likely however, to find a weak magnet on something as new as a (say 50's) 5 or 6s as it is to find a weak magnet on a 1925 model FH or a 1933 model Y.
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Old 12-21-2008, 02:24:07 AM
Bill Sherlock Bill Sherlock is online now
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Default Re: Briggs & Stratton 5S Engine No Spark

Depending on how you cleaned the points, they could still be the problem with no or little spark. In my opinion using a point file is a waste of time. What I'm using now is some fine grit (like 320 or 600) wet and dry sandpaper folded over and run back and forth between the points several times until the coating of oxidation is removed. Make sure to remove any residue that might remain between the points and then regap them to specification.

Problem could be condenser but I've found the majority of cases where an engine hasn't run for years it's oxidation of the points that's been the problem with weak or no spark.

Bill
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Old 12-21-2008, 11:19:23 AM
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grega grega is offline
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Default Re: Briggs & Stratton 5S Engine No Spark

yoy may have to gently sand the magnets and where they tuch the coil also cheak the point gap and magnet to coil gap, iv found that is usually the problem
-Greg
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Old 12-21-2008, 12:03:59 PM
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Default Re: Briggs & Stratton 5S Engine No Spark

make sure that your points are set and that the flywheel and mag coil have the right gap too far or too close and no or weak spark
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Old 12-21-2008, 08:34:21 PM
K D Redd K D Redd is offline
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Default Re: Briggs & Stratton 5S Engine No Spark

From the looks of your picture has someone SOLDERED the plug wire to the coil. The plug wire should NEVER NEVER NEVER be soldered to the coil as this can damage the coil. A good mechanical connection is ALL that is need. If there is solder, use an OHM Meter to measure the resistance of the high tention winding. One wire of the OHM meter to the spark plug wire the other to the engine. Should read 7000 to 10000 ohms. If you read an open, the soldering has damaged the coil.

Kent
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Old 12-22-2008, 12:11:13 AM
BWegher BWegher is offline
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Default Re: Briggs & Stratton 5S Engine No Spark

Contact points must be free of oxidation. The best way to maintain points is to hone with a dry india stone. It is possible to use fine sandpaper but make sure you get all the grit off after you finish. Special point files may still be available but I hate to see anyone "file" points.

Three leg Briggs armatures should measure at least 4k ohms from spark terminal to frame/ground.
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Old 12-22-2008, 10:01:49 PM
KidDynamo KidDynamo is offline
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Default Re: Briggs & Stratton 5S Engine No Spark

Try this:

http://www.smokstak.com/forum/showth...t=points+clean


I look around at garage sales for ladies diamond nail files made by Revlon, etc.

They can sometimes really work well in lieu of (or in addition to) garnet paper for removing oxides from points. Then perform the clean paper trick.

I'm closing on 50 years of small gas engine fun and I rarely need anything but points cleaning, unless there is obvious damage to a component.

I have replaced a points push rod or two and a couple coils and a condenser or two that rotted apart but most of the stuff survives pretty well if it stays in one piece and dry.

Not always, though. Happy motoring!
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Old 12-22-2008, 10:40:24 PM
whargrov whargrov is offline
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Default Re: Briggs & Stratton 5S Engine No Spark

Yes, at some time in the past some solder was applied to the plug wire at the coil. I had read that you are not supposed to have solder on that connection. I will check the coil and clean that up.

I cleaned the points again (vigorously) and now I have the following symptom. The very first pull after I put the flywheel back on, I get the most beautiful, bright sparks on the plug but on the next pull I might get a faint spark and from then on I get no sparks at all. Remove the flywheel and put it back on and I get the beautiful spark for one pull again. Could this be a flywheel key problem? The key does not look damaged to the eye but I know they can cause problems.

I am getting closer because at least I am now getting a spark on the first pull.

Thanks for all the advice.
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Old 12-22-2008, 11:57:22 PM
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Default Re: Briggs & Stratton 5S Engine No Spark

three things that are floating through my mind. First how clean is that flywheel. Is there any caked mud or dirt or something that could be hitting a part of the mag and causing dirt to fly around and get the points ditry. Also maybe you might want to replace the ponts because i beleve that they use the same style mag as the w series engine. ALso if its solderd on i would just toss the coil and do a total mag rebuild. I rebuilt mine if its the same style as a w engine for around 50 or 60 bucks
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Old 12-23-2008, 01:02:27 AM
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Default Re: Briggs & Stratton 5S Engine No Spark

Thats a long time conspericy rather to solder or not solder the coil wire onto the mag. Now from the factory they were soldered but the book say's NOT to solder due to they feared that if someone didnt know what they were doing they would simply fry that part of the coil by the heat of the soldering iron. I have done both soldered and just tied the wire to the terminal and let it be. You can do any which one you chose but the key is to not get to much heat on the terminal to fry the winding. It's a little trickey getting the factory solder off but once you do have the solder hot in a liquid state, just work the wire loose and when thats done, heat the old solder up again and brush the terminal with a fine wire brush. Thats that. Now if you do chose to solder a new ignition wire back on you just tie the wire to the terminal, hold a little heat on the terminal and touch some rosin core to the tip of the iron at the same time and feed it onto the terminal. It should just run right off onto the terminal and wire if it's good solder and then leave it be. It doesnt hurt a thing to get the terminal hot enough to solder, you just dont want the coil smoking in the process. It's like taking your time in a hurry. Im wandering about the way you describe the spark. If you have a good condencer (NEW) and the points are good and set right and there clean and you know there clean ( a quick wipe with a busines card does the trick if there not ) number one im wandering about your main bearings becouse if they are wore and you can move the flywheel up and down a considerable amount then that can be a problem becouse then you have an eratic armature air gap and that DOES make a diference. Number 2 if thats fine then it's possible that you have a coil that is dropping out. Symptoms are eratic spark, good spark, bad spark, non at all, spark missing firing cycles. There are alot of cases in the older engines that the engine doesnt exactly have to have been worked and hot to tell you if you have a bad coil. That ocasionally goes for the condencer too.

Last edited by Sky; 12-23-2008 at 01:23:31 AM.
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Old 12-23-2008, 12:58:47 PM
K D Redd K D Redd is offline
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Default Re: Briggs & Stratton 5S Engine No Spark

If you are getting some fire LEAVE THE SOLDER CONNECTION ALONE. You may damage the coil tring to remove the solder.
As others have said, Clean the magnet area of the flywheel and Clean the three poles of the coil.
The four screw the hold the coil on are in slotted holes. Turn the magenet on the flywheel so it is away from the coil. Loosen the four screws and pull the coil up as high as it will go. Tighten the screws, turn the flywheel so the manenets are under the coil. Lay a business card on top of the magenets and then loosen the screws holding the coil which will trap the buss. card between the coil and the flywheel. Now tighren the coil mount screws. Turn the flywheel to remove the buss. card and you should have the right gap for the coil to flywheel.
This took three time longer to type than it does to do the job.
Kent
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Old 12-30-2008, 10:46:28 AM
whargrov whargrov is offline
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Default Re: Briggs & Stratton 5S Engine No Spark

Well, I adjusted the spacing between the coil and flywheel, set the points spacing but still have little or no spark. Then I noticed that the screw that mounts the points bracket to the engine never gets very tight. Evidently when the shaft rotates and pushes on the points it is moving the entire points bracket and ruining the points spacing and preventing ignition. Afraid that the screw/hole is stripped. The screw looks OK to the eye. Can I use a slightly bigger screw or do I have to replace the grey metal plate that all the ignition parts are mounted too? Any other ideas?
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Old 12-30-2008, 12:36:48 PM
CJBennett CJBennett is offline
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Default Re: Briggs & Stratton 5S Engine No Spark

I've Heli-coiled them before (replaced the threads). I don't see why going a little over sized would hurt any thing either. Glad you found the problem.
CJ
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Old 12-30-2008, 12:38:04 PM
K D Redd K D Redd is offline
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Default Re: Briggs & Stratton 5S Engine No Spark

Yes, try the next larger screw. I think the original is most likely a number 6. I would try a number 8 of which ever thread count you have handy.

Kent
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Old 01-09-2009, 10:47:03 PM
Arlie Levy Arlie Levy is offline
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Default Re: Briggs & Stratton 5S Engine No Spark

I had the same problem and the keyway in the flywheel was worn real bad. I replaced the flywheel and it is fine now. Arlie
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