Reading Spark Plugs

Discussion in 'General Harley Davidson Topic' started by fxdc1951, Feb 25, 2015.

  1. fxdc1951

    fxdc1951 Member

    I've read that with today's unleaded fuels with the ethanol, and now that bikes have efi, that you can't get a plug reading anymore. They all look pretty white because the fuel burns cleaner. True?
    I've seen plugs from bikes that have Power Commanders, Serts, etc. on them and they look pretty white too. Reason I ask is because I had a PC on my last bike, and I see no difference in plug color compared to my current bike. I asked my "indy" about that, and he told me the same thing. Quote------> "Today's fuels make it very hard to tell how rich or lean your bike is by looking at the plugs. Not like it used to be with carbs and the older gasolines. Unless you're running really rich, they all look the same." <------ End Quote...... I've also seen that posted different places on the internet (so you know it has to be true! LOL).

    I still have some plugs thrown in my toolbox from my old carbed EVO. Nice and tan color.

    EFI has a lot of advantages, but sometimes I think carbs were better.
  2. drpcfix

    drpcfix Member

    Clean plugs means that the engine is running well. With a carb it was very easy to be running rich or lean so you had to look at the plugs. Why on earth would you want a carb with just two settings (idle and off idle) vs an EFI that has hundreds of available combinations to meet the need of the engine. Sure an EFI bike when acting up will get you stranded but how many EFI bikes have you seen on the side of the road because of the EFI?
  3. Bodeen

    Bodeen Well-Known Member Staff Member Moderator Contributor

    This maybe one. 2000 ultra classic mm efi wont start - Harley Davidson Forums -

    My bike has never sat on the side of the road because of its carb. I wouldnt trade it for F.I. but that's just me...:D
  4. Jack Klarich

    Jack Klarich Guest

    You will need an eye loop to read plugs a bit of light may help as well:D
  5. Jeff Klarich

    Jeff Klarich Well-Known Member Contributor

    Although it's true it is harder to read plugs used in newer cars/bikes it still can be done. Take a look at Jacks post and there's also good reads on the internet.
  6. drpcfix

    drpcfix Member

    I got a carb generator on my boat -- would trade if for a FI model in a heartbeat. Of course the issue isn't the carburetor but rather the really crappy electronic control the manufacturer rigged up to control it.
  7. dolt

    dolt Senior Member

    Echoing Jack and Jeff. The eye loop or any good magnifier is necessary to truly read a plug as well as knowing what one is looking for. The color of the insulator is just one aspect of reading a plug as the photo in Jack's post indicates.

    I have two Harleys, both with performance motors; one carbed and one EFI. One is an '02 FLHT, carbed and one an '05 FXSTDI, EFI. If I had to sell one, the EFI bike would be the one to go.:coffee