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Small Air Cooled Gasoline Engines

Briggs & Stratton Model FH that has No Spark


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  #1  
Old 10-09-2019, 12:28:44 PM
Warren Wolf Warren Wolf is offline
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Default Briggs & Stratton Model FH that has No Spark

Hi, I have a B&S model FH that has no spark. I purchased a rebuilt coil (has horseshoe coil) a new condenser and new wires. Had to get a flywheel, magnets seem fine, which I had to "fit" to the engine. So everything moves as it should. Points set at .020. When I attach a sparkplug and lay it on the engine I do not see a spark. Any ideas on what I can do or check? Thanks
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Old 10-09-2019, 02:16:09 PM
Partsman Partsman is offline
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Default Re: No Spark

You didn't say anything about the points. Most likely you looked at them and they looked good. YOU MUST clean them. Clean them with a fine abrasive 5 or 6 times and when you are sure they are clean clean them some more. get a can of contact cleaner for the finial cleaning. 99 % of the time that's the problem.
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Old 10-09-2019, 03:45:46 PM
Andrew Mackey Andrew Mackey is offline
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Default Re: No Spark

After a thorough cleaning, do this: take a clean white business card or a 3x5 and place it between the points. turn the crank until the points close and draw out SLIGHTLY, a 1/4" will do. Turn the crank or open the points manually and remove the card. DO NOT just pull it out! if the points are perfectly clean, there will be no residue on the card. Any gray or black residue, you need to clean them again, until nothing is left on the card. How strong are the magnets in the flywheel? it should take a fairly strong tug to remove a piece of steel from the magnets. If they are weak, the mag wont work. As you turn the crank, hold onto the coil wire. Do you get bit or just a tickle? Nothing at all? What kind of wire is coming off the coil? It should be a wire core wire, not modern carbon core. You stated that you had to 'make it fit'. What did you have to do exactly? The magnets need to be in close proximity to the coil to work corretly (5 to 10 thousandths max), so if there is excessive clearance between the core and flywheel, that is another problem. Are the magnets passing the coil when the points open (timing)? Lastly, are you sure you have the points and wiring installed correctly? If the insulation on the wire mounting is out of place or is shorted, you wont get spark. Here is a quick test. Get yourself a 12 volt test light and a 9 volt radio battery. ground the battery to the engine and place the aligator clip on the test light to the other side. place the probe against the block, and it should light dimly. If it does, continue. Now place it on the points wiring, with the points closed. it should light with the same intensity. Now open the points. it should nearly or completely go out. if it does not, then the points wiring is shorted at some point. Take 2 wires and attach to the battery. With the spark plug grounded on the engine, ground one wire, open the points and drag the wire across the points wires. You should get a spark at the plug, if not, something may be wrong with the coil. These are simple tests, beyond thatonly a mag shop will be able to tell you what is wrong. Could be a bad condenser (it happens), could be a shorted coil. If the engine has a kill switch, disconnect it and see what happens. Check all your connections again, sometimes its just something you missed the first time. been there, done that!
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Old 10-09-2019, 07:10:34 PM
Warren Wolf Warren Wolf is offline
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Default Re: Briggs & Stratton Model FH that has No Spark

Thanks guys, really appreciate the info. I did clean the points but perhaps not enough. Thanks again.
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Old 10-10-2019, 07:00:39 AM
I like oldstuff I like oldstuff is offline
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Default Re: Briggs & Stratton Model FH that has No Spark

I have a FI with the same ignition.
As the magnets are a bit weak it won't create a spark with a normal points gap. But it runs fine with a gap of around .009. Sure, the timing is off but to just run it it's fine.

Try closing up the gap and let us know.
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Old 10-29-2019, 06:58:42 PM
G.M.Johnson G.M.Johnson is offline
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Default Re: Briggs & Stratton Model FH that has No Spark

Also if your engine has a kill button on the side of the housing make sure the contacts aren't bent and constantly touching. Just to be sure the coil is good I would ohm it out. On the primary side you should get a very low resistance like around 1 ohm or less, and on the secondary side at least over 2000 ohms.
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Old 10-29-2019, 11:59:46 PM
whytey whytey is offline
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Default Re: Briggs & Stratton Model FH that has No Spark

Hi all
Silly question but have you tried a spark plug from a running engine that you know 100% for sure is working ?
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