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Discussion Starter #1
How much a difference does spark plug gap make?

I have 1995 266-H which has a Kohler CV16a spec 61514 624cc

The service manual is impossible to find. Its the same block size as the newer cv 18s. same ccs. They suggest .76 mm gap. I just found my owners manual and it has 1.02 mm listed. Both use champion RC 12YC plugs.

I've been using .76 mm based on the online manual (it looks just like my motor, same 624cc)

What effect does a narrower gap than recommend have? It runs with the narrower gap. Just curious on why Kohler decreased the gap on the 18hp model.

Thanks
 

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Discussion Starter #2
I went out and checked the gap. .76 so I re gaped to 1.02 mm. I did not expert much but it did change things.

The little hesitation it had on take off is gone. Also it seems to be running faster like the rpms have gone up a bit. Just seems to have a little more power. The plugs were black, maybe the wider gap burns hotter and thus more of the gas burns. Not sure on that.
 

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Hmmmmmm... I would have guessed the opposite, and apparently I would have been wrong. So thanks for posting this, I learned something new today.
 

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The larger the gap the higher the voltage required to jump the gap.

Either is probably fine, but, the narrow gap reduces the high voltage strain on the plug wire and coil.

That is why new cars have large diameter spark plug wires, to survive the high voltage ignition.
 

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Discussion Starter #5
The larger the gap the higher the voltage required to jump the gap.

Either is probably fine, but, the narrow gap reduces the high voltage strain on the plug wire and coil.

That is why new cars have large diameter spark plug wires, to survive the high voltage ignition.
Good to know thanks.

I just redid the gap to my motors spec. If you look up my motor you won't find an online manual for it. They have a cv 18 which is newer and probably has different electronics. That is why the Toro shop had been mis gaping. My mower is too old I guess.

I found this info in gaps.

"On the other hand, since a larger gap gives a "hotter" or "fatter" spark and more reliable ignition of the fuel-air mixture, and since a new plug with sharp edges on the center electrode will spark more reliably than an older, eroded plug, experienced mechanics also realise that the maximum gap specified by the engine manufacturer is the largest which will spark reliably even with old plugs and will in fact be a bit narrower than necessary to ensure sparking with new plugs; therefore, it is possible to set the plugs to an extremely wide gap for more reliable ignition in high performance applications, at the cost of having to replace or re-gap the plugs much more frequently, as soon as the tip begins to erode. "
 

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Ignition
Spark Plug Type (Champion® or equivalent) ............................. RC12YC (Standard) or
Premium Gold 2071 (Pro Series)
Spark Plug Gap
CV11-15, CV460-465, CV490-495 .................................... 1.02 mm (0.040 in.)
CV11-14 LP, CV16 ............................................................ 0.76 mm (0.030 in.)


This came directly from the manual.
 

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Discussion Starter #7 (Edited)
Ignition
Spark Plug Type (Champion® or equivalent) ............................. RC12YC (Standard) or
Premium Gold 2071 (Pro Series)
Spark Plug Gap
CV11-15, CV460-465, CV490-495 .................................... 1.02 mm (0.040 in.)
CV11-14 LP, CV16 ............................................................ 0.76 mm (0.030 in.)


This came directly from the manual.

Yes there is some confusion on the CV 16 motors. There are actually two of them. That CV16 is not the same motor as the CV16S. If you look at the pics they are clearly not the same motors. This is where the confusion came in on what to set the gaps at.

The Gap for CV16s is spec for 1.02 mm
CV16 (similar name but different motor is 0.76 mm)

I think Toro Must have made some electronic changes sometime after 1995. The motors look similar but gap settings are not the same on the older ones.

Below is a pic. That .076mm setting does not run as well on the older motors and is not the spec they have in the manual for the 266H. Can't find an actual motor manual for the cv16s just the owners manual


 
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