# Briggs & Stratton No Spark



## jimbo7825 (Jul 4, 2016)

Hello

I was hoping I could some pointers. I have MTD mower with B&S engine and it was running fine, then the next time I go to start it, nothing. When I pull, its feels like there is little to no resistance. Tried a new plug since it was an old one and same results.

So I pulled the plug, and grounded the electrode and tried to check for a spark, there was none. Took the top of the mower off and looked at the coil. Seems ok, ohm checked at about 4.7Kohm, from what I found that seems to be in the normal range. Something I noticed, it looks like there is 2 poles on the flywheel but only 1 was magnetized, is that correct?

Does anybody have any suggestions?

thanks


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## AVB (Nov 28, 2014)

Need the Briggs model and type numbers to look-up engine.

But a couple thing here. First you can't check the primary side of the ignition coil or the trigger circuit. What your checking the secondary(HV side). There only group of magnetize magnets the other are just counter weights. Also you must be turning flywheel at least 350 rpms in normal rotation direction for a spark to be produced.

Second if this is a L-head (side valve engine) is possible with the feeling no to little resistance that one of valves is not fully closing; hence, the very low compression. L-heads do tend close up the valve clearance gaps until there is none or where the valves no longer close. I have even seen a few of negative valve clearances.


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## jimbo7825 (Jul 4, 2016)

Ill get the part number of the engine then. But talking here, is it possible the HS of the coil has shot craps and hence no spark. It was testing with someone pulling on the pull cord. 

Assuming its an L head engine and with a valve not closing, sounds like valves may need to be overhauled is what I'm hearing.


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## AVB (Nov 28, 2014)

jimbo7825 said:


> Ill get the part number of the engine then. But talking here, is it possible the HS of the coil has shot craps and hence no spark. It was testing with someone pulling on the pull cord.


If by saying HS your mean the high voltage side then your test indicates that it is good. Most coil electronics fail more often than the either the primary or secondary windings. 



> Assuming its an L head engine and with a valve not closing, sounds like valves may need to be overhauled is what I'm hearing.


Although the cylinder head must be removed to service these valves the clearance adjustment is a simply square filing of the valve stem tip a very thousandths of an inch. Sometimes valve guides may need replacing and the valve seat resurface for proper mating but this not that complex of a job just time consuming. 

I have replaced several valve guides that the Briggs Go/No Go test tool indicates that they are with specs just because it is easier to do it while the valves out then do it later and that are borderline bad. When it comes to the valve guide replacement you need the correct reamers with alignment tools and they are not cheap. They come down some since I paid over $100 for mine but they are still around $60 for 1/4" version. Much better letting a shop that already has the tools do the job besides the tech will have better experience at doing these jobs.


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