installed new iridium spark plugs

[fjbiker84]

Installed a set of iridium spark plugs from RPM today.  This should be the last set of spark plugs I will ever need if they last as long as I have heard.  But my question has to do with the black soot on my old plugs.  This is a picture of the old plugs from #1 to #4, left to right, after almost 2000 miles.  #3 cylinder has always seemed to create the worst amount of soot and that is the case again.  The bike starts immediately even if it's been sitting for several weeks, runs fine, and idles perfectly once warmed up.  I replaced the ignition coils with OEM Yamaha coils about 5 years ago but it didn't make any difference - so that isn't/wasn't the problem. Carborators were rebuilt back in 2013 by a Yamaha mechanic who did install a new jet kit because he said it was running too rich - and that did help from where the bike was over the first many years I've owned the it. Is this something to worry about or should I just make a note to clean the plugs every couple thousand miles and ride on.   

[Pat Conlon]

 Are your valves adjusted? Are the carbs sync'ed? Only then...How are your hot compression numbers? Is #1 and #3 low?
How is your vacuum advance? Those plugs should be white. Disconnect the vacuum line at the igniter box, then reconnect a piece of tubing on the vacuum port and suck on it....you should not be able to draw air when sucking.

If the above is ok, then you have some carb issues. Box them up and send them to RPM.

[FJ_Hooligan]

Too much fuel.

My guess would be fuel seeping past a worn needle seat O-ring.  

Not enough to cause running problems, but enough to carbon up a plug.

Have the seat O-rings ever been replaced?

[fjbiker84]

I had the valves adjusted and carbs sync'ed at the FJMonkey garage this spring.  I did test the vacuum advance for leaks last year after reading an article on the website about how it worked and its function.  But there was no "give" when I tried sucking on the hose line.  Still, I wouldn't be surprised if the vacuum advance isn't working properly.  I'm pretty sure all the carb parts were replaced when the mechanic rebuilt them back in 2013 but maybe that is still the issue.  Thanks!

[red]

Installed a set of iridium spark plugs from RPM today.  But my question has to do with the black soot on my old plugs.  #3 cylinder has always seemed to create the worst amount of soot and that is the case again.  The bike starts immediately even if it's been sitting for several weeks, runs fine, and idles perfectly once warmed up.

fjbiker84,

Some ideas, in no special order:

What does a compression test tell you?  Dark plugs may be rich, or oily.  Can't tell, by the picture.  Care to try a can of Yamaha Ring-Free in the mix?  A sticky ring can pass a little oil.  

The spark plug high-voltage wires may be flakey, or the plug caps may be failing.  You might want to replace those things outright.  I believe that #1 & #3 plugs both fire from the same coil.  That coil may be bad, or it may have a bad ground or bad voltage lead.  I believe that you can swap the coils, left to right; if so, try that and see if the problem moves.  If it does, then you have a bad coil.  An Ohmmeter test of coils usually will not tell you much, unless they are very bad.  For whatever you read with an Ohmmeter though, it should be the same value on each coil.

If you can find a stand-off non-contact (infrared) thermometer, you may see different temperatures at the header pipes.  FJ_Hooligan may be on to it; maybe the floats are not set the same, or there may be needle-and seat problems.

This would be a good place for a borescope (boroscope).  You can take a real look into the cylinders with that gadget.  Amazon sell them for maybe US$30.00 or so.  They plug into your phone, laptop or tablet with a USB connector.  Decent ones will have lots of pixels, and an illumination control that allows you to set the brightness, at the business end.  The cable will be non-rigid, so tape the business end to a semi-rigid wire to guide it.  I use solid copper wire for that.  Most are waterproof, so the gadget may do other jobs as well.  You might be surprised at what is inside your car doors, for example.
   

[Pat Conlon]

 ....I believe that #1 & #3 plugs both fire from the same coil.....    

Negative. Cylinders #1 and #4 share the left coil and cylinders #2 and #3 share the right coil.

Firing order 1-2-4-3

[fjbiker84]

I'll keep all this in mind - probably wouldn't be a bad idea to check the compression.  But mechanically I think my engine is solid.  It doesn't smoke or use any oil.  If it was losing compression I would think it would show in a loss of performance and I don't think that's the case.  Since moving it out here to LA I really don't have a place to run it thru the gears without worrying about cars or the CHP - seems like 95% of my time is spent putting around town in heavy traffic. But maybe that's part of the problem too.   

[balky1]

So how long are those iridiums supposed to last?

[fjbiker84]

Randy said he's seen a bike go 100,000 miles on a set.

[Bezmozek]

Yup, those are great for FJ.
I have NGK iridium spark plugs in my bike for 6 years & unknown mileage. Better cold starts even with battery sitting over month with no charging.
Will never go back to regulars.