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1987 CMX250C AC
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To properly read spark plugs engine needs a good highway run.
engine is cut off, coast to side of road and pull plugs without allowing any idle time..

check the additional links at bottom of page

I don't hold a lot of stock in reading plugs unless they are carbon or oil fouled.
Can't remember the last time I looked at insulator fire ring discoloration, but remember that it was good when checked..
 

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2012 Honda Rebel 250
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125 Posts
I have never been a believer in "plug chops". I check plugs after they have at least a couple hundred highway miles on them. Don't check them right after using the choke. In your picture, the top plug shows too lean, but if it is new it may change with some miles. The plug on the bottom shows too rich, but again, if it was removed right after running the engine with the choke on for several minutes, that will not be accurate. If the air fuel mixture is correct, the insulator should be a dark brown, but not black. Also, if an engine is burning oil, it will be impossible to get an accurate reading from the plug, because it will be oil fouled.

When you say new air filter, do you mean a new stock air filter in the stock airbox, or something like a pod filter? Getting rid of the airbox and installing a pod filter will seriously lean out the air/fuel mixture. Are both plugs the same number? Plugs with a different heat will also cause inaccurate readings.
 

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Discussion Starter · #4 ·
I have never been a believer in "plug chops". I check plugs after they have at least a couple hundred highway miles on them. Don't check them right after using the choke. In your picture, the top plug shows too lean, but if it is new it may change with some miles. The plug on the bottom shows too rich, but again, if it was removed right after running the engine with the choke on for several minutes, that will not be accurate. If the air fuel mixture is correct, the insulator should be a dark brown, but not black. Also, if an engine is burning oil, it will be impossible to get an accurate reading from the plug, because it will be oil fouled.

When you say new air filter, do you mean a new stock air filter in the stock airbox, or something like a pod filter? Getting rid of the airbox and installing a pod filter will seriously lean out the air/fuel mixture. Are both plugs the same number? Plugs with a different heat will also cause inaccurate readings.
The one on the Right is still new only a few miles on it not a lot..& it's a new stock air filter.. I also don't use the choke to start it..it electric starts just fine
 
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