Black Soot on KAF400A Spark Plug - ATVConnection.com ATV Enthusiast Community



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Old 05-09-2016, 10:40 AM
Weekend Warrior
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Default Black Soot on KAF400A Spark Plug

Hey everyone,

just joined the forum. I would appreciate any feedback on the following please:

Purchased a 2007 Mule KAF400A - 4 stroke/OHV/1cyl air cooled engine with very light usage. I use it for general gardening and property work on 4 acres. Have had it for 2 years and religiously perform basic annual maintenance - spark plug, fuel filter, air filter, oil/filter. Now with 172 hrs.

Just pulled last year's plug and noticed black soot (not oil) on the electrode end. I understand this can be result of lean mixture, dirty air filter, and/or low speed driving. Air filter check was fine. I don't run it with choke closed - just to start on colder mornings. I do only run it mostly at low speeds around the property all year.

Engine stumbles and stalls when engaging F or R at startup, but seems to settle down. Once new plug is installed - she runs like brand new.

My guess is not to worry about it - just R/R the plug each year?

Thanks in advance,
ChefK
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  #2  
Old 05-11-2016, 09:59 AM
Fasteratv's Avatar
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Quote:
Originally Posted by ChefK View Post
Hey everyone,

just joined the forum. I would appreciate any feedback on the following please:

Purchased a 2007 Mule KAF400A - 4 stroke/OHV/1cyl air cooled engine with very light usage. I use it for general gardening and property work on 4 acres. Have had it for 2 years and religiously perform basic annual maintenance - spark plug, fuel filter, air filter, oil/filter. Now with 172 hrs.

Just pulled last year's plug and noticed black soot (not oil) on the electrode end. I understand this can be result of lean mixture ( no, rich mixture ), dirty air filter yes, and/or low speed driving ( yes ). Air filter check was fine. I don't run it with choke closed - just to start on colder mornings. I do only run it mostly at low speeds around the property all year.

Engine stumbles and stalls when engaging F or R at startup, but seems to settle down. Once new plug is installed - she runs like brand new.

My guess is not to worry about it - just R/R the plug each year?

Thanks in advance,
ChefK
I wouldn't worry about it yet. You mentioned that you run it at mostly low speeds, and that may never get the plug clean. Suggestion: run it a little hard every now and then...will clean the plug up a bit unless something is wrong.
See in red above.
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Old 05-11-2016, 01:39 PM
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You could also try an Iridium plug. They seem a bit more forgiving. If your "jet needle" has grooves, you could try moving the c-clip up 1 notch or if there is a shim washer or 2 on top, maybe remove 1. Much safer to be a wee bit rich than a wee bit lean. It takes a very little adjustment to change A/F in the 1/8 TO 1/2 throttle area.
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