Second Opinion Reading Spark Plugs

1578 Views 14 Replies 9 Participants Last post by WintrSol, Jul 16, 2018

ShadowRider55

Discussion Starter · Jul 14, 2018

4

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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slick nick

· #2 · Jul 14, 2018

there both rich. dirty air cleaner.

ShadowRider55

Discussion Starter · #3 · Jul 14, 2018

I also forgot to mention that both air filters are brand new, however they are not factory oem. They just fit over the air intakes. The factory air filter makes it almost impossible to work on this model bike, 2002 Vulcan 750

Eye_m_no_angel

· #4 · Jul 14, 2018

These plugs only have ten miles on them?

The front cylinder looks like it might have some oil fouling. The rear looks sort of normal for a plug with many more miles than ten. It also looks like someone has been revving the engine when it's still cool.

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cmonSTART

· #5 · Jul 14, 2018

Pull the front again in a couple hundred miles. Rear looks pretty good.

WintrSol

· #6 · Jul 14, 2018

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.

cc rider

· #7 · Jul 14, 2018

We dont know anything about the bike. New issue? How about trying a plug chop with some new plugs. When is last time carb was cleaned. I would definitely look into that front cylinder especially if thats after a 10 mile ride

hogcowboy

· #8 · Jul 15, 2018

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.

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Eye_m_no_angel

· #9 · Jul 15, 2018

You're looking at the electrode, Hog? That's a precious metal plug. Iridium or platinum or something like that. They have those weird little electrodes that look like they're a normal plug that's been worn away and is trashed.

slick nick

· #10 · Jul 15, 2018

the tips look clean i wonder if to high octane fuel would darken them like that....or the mixture screws are out to far

cc rider

· #11 · Jul 15, 2018

Eye_m_no_angel said:
You're looking at the electrode, Hog? That's a precious metal plug. Iridium or platinum or something like that. They have those weird little electrodes that look like they're a normal plug that's been worn away and is trashed.

good catch

SemiFast

· #12 · Jul 15, 2018

slick nick said:
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).

Tobacco Road

· #13 · Jul 16, 2018

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.

hogcowboy

· #14 · Jul 16, 2018 (Edited)

Eye_m_no_angel said:
You're looking at the electrode, Hog? That's a precious metal plug. Iridium or platinum or something like that. They have those weird little electrodes that look like they're a normal plug that's been worn away and is trashed.

Yes I was looking at the electrode Eye. You are probably right then since you see modern plugs way more than I. It sure looked shot to me. As TR indicates, it still might be his problem. You don't go throwing these modern plugs in anything willy-nilly. If that's what is recommended and is the correct plug for his machine then would that also mean it's fuel injected which might mean his mapping is off? If not then I think I'd go back to antique plugs just to get a good reading. Maybe y'all can read plugs that have been in a bike a long time but I can't unless it's very obvious. Like a dripping wet plug or very oily. I need new plugs and I guess these modern plugs are too expensive to have extras for just this purpose.

WintrSol

· #15 · Jul 16, 2018

They do appear to be iridium plugs, to me, which are resistor type - I haven't found any non-resistor ones. If his bike calls for non-resistor plugs, that could contribute.

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