Help Reading Plugs
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Cruiser
Joined: Oct 2011
Posts: 153
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From: Bellmawr NJ
Help Reading Plugs
Hi Guys
Can you take quick look at my plugs and help me read them, this is very new to me. There is nothing wet or sludgy, and none of the soot comes off in my hand. The left plug is the front, right is the back.
From the reference pictures I have seen they appear to be normal? Also, why do they look a little different? Thanks, I feel without a solid reference by just looking at JPEGS online, and the FSM doesn't have color.
Can you take quick look at my plugs and help me read them, this is very new to me. There is nothing wet or sludgy, and none of the soot comes off in my hand. The left plug is the front, right is the back.
From the reference pictures I have seen they appear to be normal? Also, why do they look a little different? Thanks, I feel without a solid reference by just looking at JPEGS online, and the FSM doesn't have color.
Stellar HDF Member
Joined: Feb 2006
Posts: 3,035
Likes: 17
From: Houston Texas
Back in the good old days when we had lead in the gasoline plug reading meant much more that it does today with lead free fuel.
Even then the way to do a proper plug reading was to run the bike wide open to your top speed.
Note we are talking over 100 mph here, so this is not something easy to do.
We then while going at top speed we cut the ignition off, pulled in the clutch and kept the throttle wide open until the engine died and we coasted to a stop.
If you turn off the throttle the reading is messed up to the point you cannot get a good plug reading.
If your engine is running smoothly and idling fine I would not get concerned over trying to read your plugs.
Believe me when I say I have a world of experience doing plug readings in years past and today I do not give a hoot about reading plugs because of the difficulty of doing the test.
Your plugs look fine to me.
Oily deposits on plugs tell you the you need rings and perhaps a rebore.
Black sooty deposits tell you that a rich condition exist. But that richness can be done by letting the bike idle and then doing a 'plug reading'. Not the thing to do.
Last of all, when the center of the plugs are white that indicates a lean condition which could burn a hole in a piston.
This condition is the only one that would concern me and your plugs do not reflect that condition.
pg
Even then the way to do a proper plug reading was to run the bike wide open to your top speed.
Note we are talking over 100 mph here, so this is not something easy to do.
We then while going at top speed we cut the ignition off, pulled in the clutch and kept the throttle wide open until the engine died and we coasted to a stop.
If you turn off the throttle the reading is messed up to the point you cannot get a good plug reading.
If your engine is running smoothly and idling fine I would not get concerned over trying to read your plugs.
Believe me when I say I have a world of experience doing plug readings in years past and today I do not give a hoot about reading plugs because of the difficulty of doing the test.
Your plugs look fine to me.
Oily deposits on plugs tell you the you need rings and perhaps a rebore.
Black sooty deposits tell you that a rich condition exist. But that richness can be done by letting the bike idle and then doing a 'plug reading'. Not the thing to do.
Last of all, when the center of the plugs are white that indicates a lean condition which could burn a hole in a piston.
This condition is the only one that would concern me and your plugs do not reflect that condition.
pg
Thread Starter
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Cruiser
Joined: Oct 2011
Posts: 153
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From: Bellmawr NJ
Cool. I have had it up to 100 (105 on speedo, not sure about accuracy) once but it was probably 300 miles before this reading, and yes it felt like quite a feet that I won't be doing again. Thanks for the advice though Piniongear, there is really nothing wrong with how the bike starts or runs.
Stellar HDF Member
Joined: Feb 2006
Posts: 3,035
Likes: 17
From: Houston Texas
I think you are good to go KS.
Sometimes I get a bike tuned perfect and then I always think.....well, maybe I can make it a little better.
I usually will screw it up and then have to back track to where I was at.
Once we have the machine running smoothly and starting easily the only thing left to do is ride it and enjoy it.
pg
Sometimes I get a bike tuned perfect and then I always think.....well, maybe I can make it a little better.
I usually will screw it up and then have to back track to where I was at.
Once we have the machine running smoothly and starting easily the only thing left to do is ride it and enjoy it.
pg
My plug analysis goes like this, looking at the porcelain ...
white == lean
very dark == rich
light to medium tan == good
black soot == rich
oily/sticky black == oil fouled
I check my plugs after a longish [half hour] ride at hiway speeds on back roads [to clean the plugs] followed by 5 to 10 minutes in the city on the way home [to color the plugs]; i do not let it idle after i get it home.
In my Keihin butterfly carb this basically tests the slow jet and pilot screw setting. I do not care to test the main jet as i am not a fan of WOT riding - i know it is big enough, but not so big that it causes any trouble.
In my experience the front plug always comes out lighter than the rear.
I think yours look a bit on the rich side, but that is said to be the way IronHeads run best. I would not change anything.
white == lean
very dark == rich
light to medium tan == good
black soot == rich
oily/sticky black == oil fouled
I check my plugs after a longish [half hour] ride at hiway speeds on back roads [to clean the plugs] followed by 5 to 10 minutes in the city on the way home [to color the plugs]; i do not let it idle after i get it home.
In my Keihin butterfly carb this basically tests the slow jet and pilot screw setting. I do not care to test the main jet as i am not a fan of WOT riding - i know it is big enough, but not so big that it causes any trouble.
In my experience the front plug always comes out lighter than the rear.
I think yours look a bit on the rich side, but that is said to be the way IronHeads run best. I would not change anything.
Last edited by IronMick; Apr 14, 2012 at 10:41 PM.
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