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19.5 Hp Briggs Spins Too Slow To Start, Any Ideas?

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#1 malibukid71 OFFLINE  

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Posted July 13, 2014 - 05:43 PM

19.5 HP I/C Platinum Briggs and Straton. Twin cylinder, L-head, air cooled, 42E707-2631-E1. This engine is the factory engine on my Craftsmen mower. I mowed with no issues a few weeks ago but when I went to mow last week it would not start. The motor turns over but it doesn't seem fast enough to start. I've replaced the fuel filter, both spark plugs, and now the magnito. Still spins too slow! I've tried with just the battery, the battery with a charger attached, and the battery with a jump box attached and haven't noticed a difference in the speed. I'm out of ideas with some pretty tall grass. Anyone have an idea I've overlooked. I'm not mechanically inclined enough to open the engine either. I have a video of me trying to start it but I doubt I can post it here.

#2 Cat385B ONLINE  



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Posted July 13, 2014 - 05:48 PM

If you can YouTube the video, just copy and paste the link here.

#3 superaben OFFLINE  


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Posted July 13, 2014 - 08:28 PM

How is your ground cable?  Good and tight?



What I am going to tell you is a great big no-no.  However, it is a recognized way of checking a starter for professionals. 


Turn the key off.  We are going to test the starter but we don't want the engine to start.


Make sure your battery is good and charged. 


Take a set of jumper cables and hook the negative terminal of the battery to bare steel somewhere on the tractor.  Closer to the engine the better.  A good place (if you can get to it) is the rear of the starter.  There is probably a "bump" where a bearing hides.  Clip it on there.


Carefully take the hot side and connect it to the positive terminal of the battery.  Touch the cable to the red wire running to the starter.  You should see sparks ( :smilewink: ) and if the starter is good, it will spin like normal. 


If it does not spin like normal, check your jumper connections and try it with a different battery. 


If it still fails, you have a bad starter.


If it works when you do this test, you probably have either a bad key switch or a bad solenoid.


Ben W.

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#4 JDBrian OFFLINE  


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Posted July 14, 2014 - 05:40 AM

To start with I'd check the high current wiring from the battery + to the starter and back to the battery - terminal looking for dirty, loose, overheated or corroded connections. It only takes one bad connection somewhere to reduce starter voltage to the point it won't spin fast enough. Could be your starter or solenoid is bad but the connections should be checked before replacing any parts. 

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#5 crittersf1 OFFLINE  


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Posted July 14, 2014 - 06:16 AM

Grounds, grounds, grounds. Did I mention to check the grounds?

#6 Bruce Dorsi ONLINE  

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Posted July 14, 2014 - 06:36 AM

As others have said, check the easy stuff first.


In addition to checking the connections, look at the cables to see if they are corroded, or broken.  ....It is possible to get 12v through just a few strands of wire, but there will not be enough current (amps) to spin the engine fast enough.


I have witnessed starters where the shaft bushings have worn enough to cause the armature to drag against the pole shoes or magnets inside the starter.  ....This can cause the starter to spin more slowly.  .....Sometimes these can be repaired, and sometimes they can not.

#7 DougT OFFLINE  


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Posted July 14, 2014 - 03:12 PM

Well the guys have given you some good pointers but I see one that's been overlooked. Take both plugs out and crank the engine. Does it still spin too slow? If not, then check the valve clearance. This is especially critical if its an overhead valve engine. Somewhere on here, Uncle Willie has a video of how to adjust the valves on an overhead valve Briggs engine. He had the same problem you're having.

#8 malibukid71 OFFLINE  

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Posted July 15, 2014 - 12:11 AM

I never thought to upload the video to YouTube, good call


My mower won't start, any ideas?: