# 21HP Briggs twin Deere. Battery not getting it done!



## fastline (Apr 10, 2013)

I do a lot of wrenching and electrical work but I am a little stumped here. This is a Deere L120 with 21HP twin Briggs. Battery is testing perfect and so is the starter, yet 50% of the time, when you bump the key, the engine stalls at compression and will not turn over. Once cranking, it will crank perfect and fast. 

Armature test shows 1.0 ohms on every contact. No found issues with brushes, commutator, bearings, etc. 

Bat should be rated about a 340CCA. Current/voltage test shows at the stalled condition, 300A to starter, 9.5VDC. A batt should provide 1/2 of CCA at 9.5V so that bat is certainly doing what is was advertised to do. 

OEM actually specs a lesser CCA bat. I am inclined to throw MORE CCA at it to keep the voltage higher and get more power to the starter. 


What the hell am I missing here? Why is a mower with ""65hrs" having this problem?


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## jhon (May 9, 2011)

I had all the same symptoms you had. Mine turned out to be the valves needed adjusted. (too much pressure to turn over the engine) It's real simple to check and sdjust You just search youtube for a video on how to do it.


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## Mickey (Aug 14, 2010)

My first though is, don't over look the possibility of the failure of the compression release.


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## stickerpicker (Sep 16, 2003)

fastline said:


> I do a lot of wrenching and electrical work but I am a little stumped here. This is a Deere L120 with 21HP twin Briggs. Battery is testing perfect and so is the starter, yet 50% of the time, when you bump the key, the engine stalls at compression and will not turn over. Once cranking, it will crank perfect and fast.
> 
> Armature test shows 1.0 ohms on every contact. No found issues with brushes, commutator, bearings, etc.
> 
> ...


About 300 A is what the starter is designed for max. so even a 600 amp battery isn't going to change that. Begin by checking the valve lash as recommended so the compression relief has a chance to work as designed.

65 hours may be a little premature but probably not unheard of.


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## fastline (Apr 10, 2013)

Forgot to report back. Repaired last night. ran the valves and works perfect now. I forgot all about the decomp on these engines.


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## stickerpicker (Sep 16, 2003)

My lawn tractor probably has the same 21 HP engine with a little over a hundred hours and I should go check the valve lash. Then I set in this chair on my lazy butt thinking of all the valves I set on V-12 engines with 4 valve heads before retirement and a quick calculation jumps up somewhere around probably 10 to 12 thousand. So I just settled back in the chair saying to self , I'll probably just put that off like everything else and wait for it to fail.


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