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Second Opinion Reading Spark Plugs

2K views 14 replies 9 participants last post by  WintrSol 
#1 ·
I could use some advice fine tuning my bike. She starts and idles fine. After she warms up for a minute and I drop her into first gear I get some hesitation and sputtering at lower RPM ranges from 2 to 3 rpm. This is consistant in every gear I am in. Runs good around 4 rpms.

After a 10 mile ride I pulled the plugs to get a reading. Attached are some shots of the front and rear plugs. I suspect the front cylinder looks a bit rich. But I could be completely wrong.

Anyone else have some thoughts. The coils have been tested and they are all good. Also compression on both cylinders is 120 psi.

As you can see the reading are not consistant. The front spark plug seemed much darker, almost wet looking.

The rear one was browner and seemed hotter to the touch.

Any thoughts would be helpful.
 

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#6 ·
Give them some more miles after a full warm-up, at a relatively steady speed. If the oil doesn't clear up on the front, you may need a hotter plug. Running a lot around idle, or slow/fast/slow (city roads), will make them look like it is running rich. In any case, you may want to check the fuel levels in the carbs.
 
#8 ·


That plug only has 10 miles on it???? It looks shot to me with several thousand miles. I'd try new plugs and possibly even new wires depending on how they look. Then ride it at least 20 miles hard and look at the plugs then. I wouldn't try reading anything with those plugs. Plugs are relative cheap and can change how a bike runs a LOT.
 
#12 ·
the tips look clean i wonder if to high octane fuel would darken them like that....or the mixture screws are out to far
I was trying to determine if I was seeing a little bit of pink color on the center insulator of the rear spark plug. If that is pink I'm seeing that might (or could) indicate too low of octane, or maybe 20 other things...

Anyway, if those were new plugs that only have 10 miles on them... They should not have that many deposits on them.
Maybe too much fuel or possibly too much oil getting to them, or both.

Pod air filters? How many steps above stock are the main jets?
Is the carb sync set correctly? If the sync is way off that could give odd plug readings when running lower RPM. (Thinking of the front cyl plug here).
 
#13 ·
I made a one time mistake of installing Harley's Screamin Eagle Performance Spark Plugs. They look similar to the ones in these photographs. They were garbage, at least in my bike. The engine would not rev over 3500 RPM and actually shutoff twice while limping home on the Interstate. I installed a new set of NGK and the bike ran like a dream. Don't know if that could be this guys problem but it sure as hell was mine.
 
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