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Cast Iron 16Hp Briggs Backfires


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#1 BillTribbitt OFFLINE  

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Posted November 25, 2013 - 04:21 PM

      The motor on my 990 backfires when I try to start it. I assume it's just running too rich? what else should I check? Gonna post a pic of my carb spring set up later. I'm thinking the problem may be there.


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#2 glgrumpy OFFLINE  

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Posted November 25, 2013 - 04:23 PM

Point gap changes timing. Point gap is fairly hard to set with lock-nut and tight spot to work. I would clean those and reset. They are very fussy!  Think .020 is spec for new and .018 is for used. Work slow and careful setting.


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#3 HDWildBill OFFLINE  

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Posted November 25, 2013 - 05:12 PM

I was also thinking timing.  glGrumpy basically covered it.  May want to do a visual inspection of the coil, wires and connections and make sure they are all good.


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#4 hamman OFFLINE  

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Posted November 25, 2013 - 05:18 PM

Yup......gl and HD nailed it. That is why my Homelite sat idle for a couple of years. I just wasn't smarter than the points. As stated take your time in adjusting them. It may take some time but you will get it. Roger.


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#5 olcowhand OFFLINE  

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Posted November 25, 2013 - 05:54 PM

Also, if been running rich, be sure to replace the spark plug.  A gas fouled plug CAN or WILL cause backfiring.


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#6 superaben OFFLINE  

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Posted November 25, 2013 - 06:24 PM

I think between Bill, GLGrumpy and Daniel, you have the answers you need.

 

Ben W.


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#7 BillTribbitt OFFLINE  

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Posted November 25, 2013 - 09:06 PM

If I hold the governor down it will start but I get oil flying out of these 2 holes in the first pic. It that suppose to happen?

The springs must be wrong because even with throttle at idle, the spring still pulls the governor up. Should there be any tension on the governor at idle?  

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#8 olcowhand OFFLINE  

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Posted November 25, 2013 - 10:16 PM

If I hold the governor down it will start but I get oil flying out of these 2 holes in the first pic. It that suppose to happen?

The springs must be wrong because even with throttle at idle, the spring still pulls the governor up. Should there be any tension on the governor at idle?  

 

 

Oh then, the points have been totally removed.  Someone has changed the polarity of the flywheel magnets to use a Magnetron pointless ignition coil.  Find some screws to plug those holes up.  The backfiring could be that the flywheel key is sheared.

 At idle setting (with engine running), the governor should hold the throttle idle screw against the idle stop, but with engine off, the throttle will be pulled open.  Your governor is either out of adjustment, or governor is shot.


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#9 BillTribbitt OFFLINE  

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Posted November 25, 2013 - 10:18 PM

Any idea what size screws? how long? Hate to screw into something important!!!!


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#10 BillTribbitt OFFLINE  

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Posted November 25, 2013 - 10:20 PM

if governor is shot, what then? rebuild?


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#11 EricFromPa ONLINE  

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Posted November 26, 2013 - 12:47 AM

I'm betting that someone did not repolerize the flywheel magnets.The newer Magnetron pointless ignition coils will not work with a points engine until it is done.

It will start and try to run but will backfire and run extremely hot because the timing is way off.Do not continue to run it until you fix it or you will burn the valves up.

 

You have 2 choices.1 buy a set of points and a Points mag or 2 send the flywheel in to have it repolerized.

 

 

I went through this on my MTD Fourteen Hundred.I ended up just breaking down and buying a set of new points and a points coil.I would suggest getting a Nova II ignition module to replace the points But they do not work on a flywheel with more than 1 magnet.Your flywheel should have 3 magnets.


Edited by EricFromPa, November 26, 2013 - 12:51 AM.

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#12 BillTribbitt OFFLINE  

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Posted November 26, 2013 - 06:21 AM

I've had it running several times and it seems to run pretty well when it starts. One other thing I've noticed. It cranks a bit slow with the throttle up but if you hold the governor down when cranking, it turns over faster and seems to start easier.


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#13 EricFromPa ONLINE  

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Posted November 26, 2013 - 06:02 PM

Does it kick back when you try to start it?



#14 BillTribbitt OFFLINE  

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Posted November 26, 2013 - 07:06 PM

I guess I need you to define "kick back"



#15 BillTribbitt OFFLINE  

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Posted November 26, 2013 - 07:10 PM

no backward motion when you turn the key but when you let go it does rock back a small amount. That's due to compression though isn't it?






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