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Author Topic:   Odd Spark Plug Problem
Dirt Forum Champ
Total posts: 874
posted May 31, 2005 08:31 PM  
I pulled the plugs from my new motor today. All of them but #1 were fine. #1 was wet and dark, but no carbon. The top of the piston had a nice brown coloring to it (First night on fresh build), the plug had spark, but the motor missed just a touch here and there.
The plug is an AC-R43T... I can wiggle the ceramic in the actual plug..

I checked the cylinder for compression and it's doing fine on that.
Any clues?

Dirt Forum Champ
Total posts: 578
posted May 31, 2005 08:56 PM  
you shouldnt be able to wiggle the ceramic. sounds like you have a bad plug. i've seen that happen before.


Dirt Forum Champ
Total posts: 874
posted May 31, 2005 09:51 PM  
Did some more checking, opened the exaust valve all the way, piston barely has any burn pattern to it. Pulled the headers, exhaust valve was black... I'm wondering if the plug was bad but yet fired just enough to burn a little. It is the only plug that the ceramic wiggles in, when you put the plug up to your ear and wiggle, you can hear something inside the plug itself. I'm going to buy a new set of plugs, preferrably Champions or Autolites with the big end on them...

Dirt Full Roller

Total posts: 29
posted June 01, 2005 05:51 AM  
Definitely replace that spark plug.

Dirt Freak

Total posts: 205
posted June 01, 2005 06:50 PM  
Just as a personal thing but I have never had any luck with AC plugs. its been hashed on here numerous times but I truly believe NGK makes a far superior plug, especially in a full load situation. in methanol, high compression 14 to 1 and up and being fat with injection I would notice the AC's would tend to miss and flat quit alltogether on occasion. I started with NGK and just outa curiosity I had went to a 3933 simply because they were easier to work with around the headers. needless to say i'm using NGK and I'd use a very used NGK before I used a new anything else, but alas it is just an opinion...

Dirt Full Roller

Total posts: 43
posted June 02, 2005 06:38 AM  
I love my ngk plugs. I run the UR4

Dirt Forum Champ
Total posts: 2007
posted June 02, 2005 06:53 AM  
NGK here as well...

Dirt Forum Champ
Total posts: 874
posted June 02, 2005 11:23 AM  
What plug will I want to run with the 441 Head Casting? Looking for something not super hot, but decent heat.

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