Different Looking Plugs
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Joined: May 2010
Posts: 77
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Different Looking Plugs
Yesterday, going around a turn, like 60, bike cuts out for a second, comes back to life.. then 5 miles later or so, started to loose power a bit, and by then i was home... figured i would check the plugs, cap for venting (which it was) and behold, the plugs looked a little funky, but not real bad, just not matching. so, i wanted to see if anybody out there who is great at reading plugs could give me a few ideas? - by the way, after putting in new gapped plugs, she ran great again, rode about 100 miles today, perfect - from 2,000ft to about 7,000 - no problems..
the plug on the left is out of the front, right on from the rear -
1988 FLHS - mikuni carb, ev3 cam (i think)
the plug on the left is out of the front, right on from the rear -
1988 FLHS - mikuni carb, ev3 cam (i think)
Road Captain
Joined: May 2011
Posts: 684
Likes: 9
From: Indian Head, PA
I'm not a plug expert, but it looks to me like the front ceramic might have cracked. It looks deteriorated which means it might have shorted out. If it indeed shorted out, then that cylinder wasn't firing 100% which would explain the almost-fouled look to it.
Banned
Joined: Jul 2010
Posts: 853
Likes: 19
From: Melbourne
Swap them out for new ones....That front one should not have wet oil type stains on it - thats normally a bad thing; the only thing is that i do not know what it means is wrong.
I'm also worried aboutt he small bubble like marks on the centre ceramics. If theya re bubbles then its a sign of another problem (pinging/lean/overheating i think). There are some bloody good web sites around that have pictures of plugs as examples that you can compare to (so long as they are from a 4 stroke engine they will be good)
I'm also worried aboutt he small bubble like marks on the centre ceramics. If theya re bubbles then its a sign of another problem (pinging/lean/overheating i think). There are some bloody good web sites around that have pictures of plugs as examples that you can compare to (so long as they are from a 4 stroke engine they will be good)
Dirt don't hurt
Joined: Jan 2011
Posts: 21,065
Likes: 4,561
From: Haslet Texas
Keep in mind that the rear jug runs hotter than the front one.
http://www.4secondsflat.com/Spark_plug_reading.html
http://www.4secondsflat.com/Spark_plug_reading.html
Cruiser
Joined: Nov 2006
Posts: 206
Likes: 5
That rear plug shows signs of overheating, which probably contributed to the bike cutting out. This just happened to me this summer. 100 degree day, and I was lugging the engine
against a headwind fully loaded. My plug that quit looked very similar to your rear plug, although not as severe. Additionally I was running ethynol, and had just filled up at a "suspect" station (out in the middle of nowhere) 30 minutes previously. I run premium, and sometimes use an octane booster now, depending on the temps, quality of gas, and load. If I pulled the front plug out of my bike as it appears in the pic, I would wonder if IT was the one that quit or cut out and became oil fouled. Put new plugs in as you did, and pull them out at the end of a ride, and repost some pics.
against a headwind fully loaded. My plug that quit looked very similar to your rear plug, although not as severe. Additionally I was running ethynol, and had just filled up at a "suspect" station (out in the middle of nowhere) 30 minutes previously. I run premium, and sometimes use an octane booster now, depending on the temps, quality of gas, and load. If I pulled the front plug out of my bike as it appears in the pic, I would wonder if IT was the one that quit or cut out and became oil fouled. Put new plugs in as you did, and pull them out at the end of a ride, and repost some pics.
Stellar HDF Member
Joined: May 2009
Posts: 2,856
Likes: 127
From: Middle of Kansas
I may be missing something, but they look pretty good to me. The front one is a little darker color than I like mine to run, and the rear one is maybe a little light. You might want to check your intake and carb seals to make sure it is not leaking in a little air on the rear. Other than that, depending on how many miles are on them, they look OK. The rear plug will generally run a little lighter than the front.
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Road Master
Joined: Apr 2009
Posts: 1,123
Likes: 43
From: NJ
They are not similar at all and they should be. I think the one shows some sort of oil issue, it's a tad wet, and both have odd looking insulators. Do you consume much oil between changes? There are a bunch of sites out there with intructions and pictures on how to read plugs, I'm no expert.
I noticed yours were autolites, my favorites. Here is a recent pic of mine-(rear on the left), bike runs strong, 40mpg and if I take it easy I get more, plugs have over 20K on them. They show a little rich but they are leaner when I chop the ignition or run lower octane gas when it's cooler out.
I would check into why that one is wet and also the intake seals.
Ds
I noticed yours were autolites, my favorites. Here is a recent pic of mine-(rear on the left), bike runs strong, 40mpg and if I take it easy I get more, plugs have over 20K on them. They show a little rich but they are leaner when I chop the ignition or run lower octane gas when it's cooler out.
I would check into why that one is wet and also the intake seals.
Ds
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Advanced
Joined: Jul 2012
Posts: 51
Likes: 0
From: upstate ny
They are not similar at all and they should be. I think the one shows some sort of oil issue, it's a tad wet, and both have odd looking insulators. Do you consume much oil between changes? There are a bunch of sites out there with intructions and pictures on how to read plugs, I'm no expert.
I noticed yours were autolites, my favorites. Here is a recent pic of mine-(rear on the left), bike runs strong, 40mpg and if I take it easy I get more, plugs have over 20K on them. They show a little rich but they are leaner when I chop the ignition or run lower octane gas when it's cooler out.
I would check into why that one is wet and also the intake seals.
Ds
I noticed yours were autolites, my favorites. Here is a recent pic of mine-(rear on the left), bike runs strong, 40mpg and if I take it easy I get more, plugs have over 20K on them. They show a little rich but they are leaner when I chop the ignition or run lower octane gas when it's cooler out.
I would check into why that one is wet and also the intake seals.
Ds
Road Master
Joined: Oct 2011
Posts: 957
Likes: 2
From: Carlsbad Springs Ontario
Plug on left side of pic. has what looks like a solid deposit on it and would cause a missfire for sure . Also looks wet from oil contamination.
Other plug looks like its been running very hot with the grayish stain on the porcilyn.
Noticed you are running a V notched type of plug and in my opinion they are not the best .
Suspect you are burning oil in the front cyl. and possibly an air leak into the rear carb. manifold connection to the rear cyl.? Check your voes switch for ok operation.etc.
Check for air leaks in the carb. manifold and repair as needed , install standard new gapped plugs. Do a test by doing this ... Ride bike as normal until op/temp. is acheived ,
when you get close to home , go full throttle and then cut out motor and throttle at same time with closed throttle and kill switch . Roll into home and remove plugs .
Read plugs after full throttle and cut out and they should tell you what is going on inside the motor.
Other plug looks like its been running very hot with the grayish stain on the porcilyn.
Noticed you are running a V notched type of plug and in my opinion they are not the best .
Suspect you are burning oil in the front cyl. and possibly an air leak into the rear carb. manifold connection to the rear cyl.? Check your voes switch for ok operation.etc.
Check for air leaks in the carb. manifold and repair as needed , install standard new gapped plugs. Do a test by doing this ... Ride bike as normal until op/temp. is acheived ,
when you get close to home , go full throttle and then cut out motor and throttle at same time with closed throttle and kill switch . Roll into home and remove plugs .
Read plugs after full throttle and cut out and they should tell you what is going on inside the motor.