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Gone.
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17,857 Posts
They look used but still serviceable, from what I can see in the picture. Look closely at the tip though to make sure there's no pitting which can't be seen in the picture.

On the other hand, spark plugs are only a few bucks a piece so I probably change mine more then I need to. Use some anti-seize on the threads if you replace them.

What else needs changing depends on what the miles are on the bike and what service is called for at that mileage. Check your shop manual for a service interval listing. At the minimum it's good practice to check the tire pressure, check over the brakes and driveline, check the fluids, and make sure the air filter is clean.
 

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American Legion Rider
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23,631 Posts
Plugs are one the cheapest replacement ideas you'll find. So yep. Personally I'd change the plug wires too. Anything else and you have to say exactly what you are doing. Restoration of a new find or just a tune up getting ready for spring rides.
 

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Registered
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1,133 Posts
hey, take a look at the rust on those. If you put that rust on my bike I would skin you alive, feed you to the local cannibals, and then burn your colors.

new is plenty much better than rust. even if they work, you did wonder enough to ask.
 

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Premium Member
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8,960 Posts
Plug it

Look at the center core. The top plug is white and the lower plug is grey.
The top plug is running a bit lean.
Put in new plugs, run it WOT if you can, then stop the engine and check the plugs. Maybe one cylinder on your kind of bike does run a bit leaner than the other.

Unkle Krusty*
 

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Ace Tuner
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2,938 Posts
Yes, change those rusty plugs. The spark plugs in the pic are cheap to replace so why not?
I change mine before they need to be changed. Keeps it running nice and sharp.
Looks like I can see some build-up(?)on the ground electrodes too. (Possibly burning a little oil)?

Cars have resistors built into the plug wires. Japanese bikes use steel core wires with resistors in the plug caps.
Very rare that the wires go bad. The resistor in the plug caps can and do fail from time to time.

BTW, NGK (like in the pic) is the correct brand for Japanese machines.
 

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Registered
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1,133 Posts
they look like they have been firing... a firing plug is a good plug.
did you test the coils? you know, pull the plugs out and hold them against the case?
you know...
YEE YAH YOH

that one is ok....hitting every time.
 

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Gone
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23,907 Posts
they look like they have been firing... a firing plug is a good plug.
did you test the coils? you know, pull the plugs out and hold them against the case?
you know...
YEE YAH YOH

that one is ok....hitting every time.
You aren't supposed to test them with your tongue.
 

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3,160 Posts
In my experience with one particular bike that was running lean, a white deposit on the plug kept the bike from firing.It only took 200 miles of deposits to foul the plug. I had to but new plugs to get home. So yeah, change plugs as a diagnostic tool. You can clean them for re-use later, but those look nasty and I would discard them.

I quit riding that bike until the carbs were cleaned as I was afraid of melting a piston.
 
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