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It ain't broke... but?


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Kent, sometimes you can get rid of the run-on problem just by running a higher grade of fuel. I've hed this problem in several of my vehicles in the past and this usually does the trick unless the idle speed is set too high. It seems the gas companies keep changing the formulation of gasoline which isnt always the best and can cause problems such as pre-ignition, run-on, deposits, deterioration of fuel system parts, etc. AdamF
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Run-on is not good - it should shut off at any speed - it's just that some will backfire when shutting them down with todays gas and idling down might help that. You just might want to check that head as you said there was serious neglect. Another thing that could cause a rich mixture is a weak ignition (besides the obvious weak coil or condensor and worn points) is oil contamination getting onto the points. Check for a worn point plunger and/or bushing, a missing little rubber "boot" seal, and that the breaker plate mounting screws have pipe dope or oil resistant sealer on them as they are threaded all the way into the block. This is commonly over looked but it is very important to keep the points clean. And even if this is not the problem it is good to know about. After all - a happy tractor makes a happy owner :)
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I haven't experienced pre-ignition (thank goodness) but it would sometimes "diesel" or "run-on" when hot after I turned the switch off. After seeing earlier posts, I've started dropping the throttle down to idle for a few seconds before I shut it off, and that seems to have stopped that....

Any other symptoms of carbon buildup that I should look for?

Based upon my experience to date, I'm inclined to leave well enough alone (since every project I seem to get into is 3 times as much hassle and 3 times as expensive as I originally estimated), but I certainly don't want to cause a problem by neglecting the symptoms. (It concerns me that this is considered "routine maintenance" yet I've never done it.) I'm slowly trying to overcome previous neglect on this fine old beast....

Meanwhile, I'll try DLC's tip on checking the manifold/head/carb connections....

Thanks for the continuing input -- it's great! That's why I started this whole club/website thing -- so I could talk to others who know so much more before I tried something...

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Check the ign. timing -not set right[that includes proper point gap], or the combustion chamber has a 'glowing' hot spot[sharp edge,or carbon build up]also check to make sure the right heat range plug is used,J-8 or CJ-8 Champion or equivalent brand. Sounds like you have something inside the combust. chamb. that is getting red-hot and continues to run the eng.after the plug is shut off!And yes if allowed to continue,will damage the piston and rod. dlc
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My Big Ten purchased new by my uncle in 1965 has never had the head off for decarbonizing nor have I experienced any problems with this engine such as you describe. I am an auto mechanic by trade and in no way consider myself an authority on small engines. I therefore submitt the following for your perusal and coments from those more knowledgeable than myself.
Due to the obvious costs of removing cylinder heads from automobiles to remove carbon deposits caused by the dirty fuels we are forced to use today several products have come on the market that do an excellent job of cleaning combustion chambers. Wynns has a three step process that works well and there are several others. Perhaps someone has tried one of these processes and could comment on the results. Water injected as a mist into the carburator air intake or though a vacumn tap on the intake manifold also has the ability to clean carbon deposits although not as rapidly as the cleaners. Cleaners made to add to the fuel tank will do little to help clean carbon. They have to be a weak formulation to prevent damage to the fuel system.

I consider it a sin to shut down an engine without an idle period to stabilize temperatures and never shut down above an idle unless an emergency.

My humble opinion, Alan
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I apoligize for the smug remark about "if it ain't broke...
A.This is from the guy who pulled his blades, spent time and effort
in putting on the perfect edge angle, and carefully balancing
them, then promptly reinstalled them UPSIDE DOWN.
B.Decided a complete tuneup would be nice, and ALMOST bought a
new coil (@$90.!!), when the problem was really the new plug wires
weren't shoved into the coil far enough.

I've been dreaming of chrome plating my front axle next......
I REALLY need to change the hydro oil and filter. I can just imagine the circus that
will ensue.

The old Kohler starts great now, and doesn't burn oil,
but that 19 hp is not afraid of burning gas.
Nice thing though, it just loafs along, hardly ever
hitting the govenor.
Sort of like it's owner.

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