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Gravely 8123/K301 pings, chugs, and dies w/difficult restart, when modestly loaded - FIXT

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Stumpy McGrinder
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2015/12/04 13:27:18 (permalink)
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Gravely 8123/K301 pings, chugs, and dies w/difficult restart, when modestly loaded - FIXT

,When searching for a fix for this, I found many other in the same predicament, and many "maybe its" replies.  I can now say "been there, fixed it!"
 
When the ping-chug-die mode starts, it usually starts with a modest overload condition.  The governor detects a drop in engine speed and opens the throttle a bit more, the engine pings and dies, then the governor opens the throttle to "full".  Disengaging the PTO and traction clutches do little or nothing to help recovery.  Moving the throttle to idle helps... for some.
 
There are two problems. Throttle, and advanced timing.
 
First the throttle.  Moving the throttle to idle will absolutely help for recovery.  The reason this works for some but not other owners is the throttle/governor mechanism may or may not be getting the carburetor completely closed to idle position when the operator moves the throttle to "Min".  When you have a look at the throttle/governor linkage, you can see that there are tension springs that are stretched when the throttle position is in the "Max" position.  But, in the "Min" position, the linkage seems to rely on "pushing" the already relaxed tension springs to close the carburetor/butterfly.  Perhaps this arrangement works on some models, perhaps my engine was missing a return spring... 
 
If you do not have a return spring at the carburetor, then add one.  There is even a small hole in the corner of the K301 fan shroud to tie it to.  Just bend the corner out to attach.  The other end of the return spring needs to attach to the butterfly control such that it tends to close the butterfly.  "Tends to close" means just that, the spring needs to be wimpier than the other springs in the linkage such that the linkage can still open the butterfly against the force of the return spring.  The throttle cable may also need to be adjusted such that the operator can set idle and full power range.
 
The pinging is from the timing being advanced.  This happens when the points gap has worn and is too large.  Large gap is less dwell, and advanced spark.  The book says set the points to .020".  As the points wear to .024", the timing advances, and well, you are back to where you are now.  There is some tolerance on that setting, so use it!  Set the points to .016" and let'm wear to .020".
 
Worn points will not have flat contact surfaces and will not gap properly.  Worn points set with a feeler gauge to .020" may actually (continuity wise) be .030", or more.  No points on a Sunday afternoon??  Resurface, reinstall and set the old ones.  Then, order some new ones, P/N 4715003S. 
 
Two more things.  1) Why does Kohler use a 12 volt coil and no current dropping resistor?  2) Will installing a coil ballast resistor increase points life?  I don't know the answer to either, but I installed one anyway.  The damn thing runs great, better than it ever has since I have owned it!
 
EDIT: 30 Dec 2015, add coil ballast resistor info.
Ballast resistors available from AutoZone, (about $5)
P/N           Ohms
CR139         0.5
AL795        0.633
CR107        1.25
F795           1.4       <<------  Suggested part to use.
post edited by Stumpy McGrinder - 2015/12/30 13:58:00

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