Spark plug- dry fouling? (pic)

Discussion in '2-Stroke Engines' started by Fletch, Oct 26, 2010.

  1. Fletch

    Fletch Member

    According to what I've read about spark plug color, it looks to me like my plug has some carbon build up or dry fouling. It seems to be running really well, but really hot. I have had a large degree of variation in fuel richness on this plug, so I don't know when it developed this gray color.

    I'd like to know what you guys think about the color, what it means, and what I should do. It's a $7 NGK BPR6HIX I got from SBP. Can I still use it? should I just throw in a Chinese plug, see what color it is, and then trash this one?

    I gapped it to .36, not knowing if it should be different than the Chinese?

    Attached Files:

  2. geebt48cc

    geebt48cc Member

    Yes, sure you can still very much use the NGK.....

    What mix ratio? Needle notch position? Air leaks?

  3. Fletch

    Fletch Member

    Right now I'm running 40:1, but I used this plug at 20:1 before when I was trying to get my carb fuel/air right.

    I'm using a cns 'speed' carb and the clip is 1 notch from the lowest. It came 2 notches from the lowest but it seemed like I was getting delayed response when I turned the throttle so I moved it down.

    I don't believe I have any air leaks but I haven't checked yet. I'm just concerned that I need to get the plug to the ideal 'tan' color to avoid engine damage. After running the bike tonight, and idling it for a minute afterward it was smoking from the exhaust. It is still in the break-in period. I may go to 30:1 next tank.

    I got this info from the NKG site about fouling. My plug isn't as dark as the one pictured.
  4. geebt48cc

    geebt48cc Member

    Total miles? See, you've got it gapped pretty high at .36? It should be .20 to . 28........... Listen, use search icon here, that should help also.

  5. arkives1

    arkives1 Member

    spark plug dry fouling?

    You didn't say what engine you're running, 2 stroke or 4? It seems you are running a very light oil mix depending on the engine. Especially during break in. Is your muffler clogged? If you're running a high capacity air intake and the muffler can't exhaust it with the correct back pressure you'd get performance problems. Possibly that carb is not a good match for the engine or is running rich despite the higher air intake?
  6. Fletch

    Fletch Member


    New build, second tank of gas (very low miles). You're right about the gap. I did everything initially according to spooky directions, which said to gap the Chinese pluig at .36. There were no instructions for gap on the NKG, but just last night I read (after using the search icon :grin5:) "you should never gap an iridium plug" just after watching a NGK video about how to gap NKG iridium plugs lol. So today I will set the gap back to the factory on the NKG (.18) or maybe .20 after what you said? The NGK video said to never use a traditional gap tool because you can break the tip easily on the iridiums, so I may go buy a better 'feeler' tool.

    BTW, I use the search constantly (my favorite icon!), but only turned up one thread about a "gray plug". That's when I started searching the net.


    Well I did post in the 2 stroke forum :grin5: JK... yeah it's a 66cc skyhawk.

    Again you're right about the oil mix. I had it at 20:1 and was still having issues with getting the bike to perform well. I was reading up on oil ratios here and it seems there is no set consensus...more personal opinion/controversy. I read the argument about 40:1 being used in all 2 strokes and it looked convincing so I tried it out, and I noticed a big difference- ran much smoother. I was was running too lean at 20:1, and I had a bunch of oil dripping out the exhaust which I read is normal, but I wasn't a big fan. I'm going to compromise and change it to 30:1.

    I don't believe so. Not sure how to check, but I'll do a search.

    This CNS 'speed' carb comes with many of the Grubee kits now, and has an extended Z intake to get around the seat tube. Some people love them, and some hate them. I'm undecided because they do require much tweaking IME so far.

    Like I said... I had/have the bike running well. Maybe the excessive heat and smoke is par for the course. I was surprised how hot the plug boot was though 10 min after killing it. The plug has 2 great reviews on Sick Bike P where I got it.

    I'm going to do some more tweaking, but I have one main question:

    Even though the NGK plug can still be used after what appears to be some fouling from carbon build up.... Should I use a new white plug and test it every time until I achieve the desired tan color, and then switch back to the NGK so I know my engine is running at the correct air/fuel and have the peace of mind that I won't damage my engine eventually?
    This tan color is pretty important from what I've read.

    Thanks again guys, I appreciate it. I'm learning a lot as I go, and spending hours on this forum which is a life saver.
  7. arkives1

    arkives1 Member

    spark plug dry fouling?

    Hey, we're ALL still learning! I'm using stock mufflers and carbs on mine and still running great after about a year of riding. I do get a nice tan color on both bike's plugs. I started running mine at 32:1 after about 150 miles for break in and both do nicely with it. I have two mopeds that run on 50:1 as does my outboard engine on the boat but those are better engineered engines.
    I hope you get all the help you need here.

  8. Fletch

    Fletch Member

    Thanks Larry,

    I just switched from 40:1 to 32:1, put back the stock plug, and put the carb back to the "pre-adjusted" settings it came with. Started it up. Didn't idle. Turned back the air/fuel screw a little and now it's running great!
  9. arkives1

    arkives1 Member

    Sparkplug dry fouling?

    YAY! Glad to hear it's working well now. Let's hope it stays that way. There are lots of good guys on here willing to help any way they can. They've certainly helped me a lot and I've made some good friends along the way.