What's up with this one plug?

Yama49601

Yama49601

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Joined
Jan 5, 2006
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896
Age
51
Location
Cadillac, Michigan
Why is the insulator so black on this one spark plug when the other two are still white? The carbs are all set the same.
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From left to right is PTO Center and Mag.
 

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I hope thos are new plugs, if not that thing is in burn down territory,

obviously that cyl. is running rich it looks like..
 
those 2 that are white are awfull lean looking, the rich PTO side would be better to have then the other 2 look, the burn is past the bend on the ground strap and I can see silver on the elctrode center, just from the pic, its hard to tell from a pic because I cant see all the things I like to look at when reading plugs but it looks too lean in 2 cylinders.

many things come into play when reading plugs, such as the way they were run, how the sled was stopped, did it tidle after the WOT run? this will all change the readings.If you look down in the cone of the insulator on the 2 white looking plugs, is there a dark circle or ring about halfway doen the tapered part of the ceramic?
 
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They are new. Only ran a couple miles I'm just trying to get an idea of what I need to do as far as getting this thing jetted right since I put these pipes on. The mag plug is dark on the insulator down from that white, about 2mm of it are white and the rest is dark. The center plug has that white about 1.5mm down the insulator and the rest of it is dark. It was pretty damn cold here last night when I ran it (about -10F). Why are the center and mag plugs running so much leaner? I have the needles at 3.5, 4 and 3.5 (well I think that's the numbers pto and mag are raised 1/2 from stock and center is a full). It's got 150 mains and 52.5 pilots. The fuel screws are all currently at 1 1/2 turns out.

Oh, it did idle too. I don't have a big enough area to run WOT for more than a couple seconds close to here.
 
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most likely the needles are lean then , the pilots and fuel screws should be good, and if you cant run it wide open for very long your mostly on the needles then, thats where I would start with it.
 
First, are you sure the carbs are clean (all circuits) ?

Not to contradict anyone on here, but if you only ran a couple miles then there is not enough coloring on a new plug to read much. The PTO is awful dark for having only run a couple miles.

Don, what would say about trying to read new plugs with only a couple miles on them?
 
I'd say get a pison light and check the wash on the pistons. But I'm not a very smart man jenny LOl Maxdlx
 
Well I just went over and tried it again since it's about 30 degrees warmer than it was last night when I was messing with it. Now that PTO plug is just fouling out. Could this be a weak coil? I wonder about that because this cylinder has always ran richer than the other two since I bought it last year. For some reason that cylinder is jacked. I called Bender and he told me to try setting the spark plug gap at .025 and to change that pilot from the 52.5 that I have in it now to a 50. I just went to the dealer and ordered one but it won't be here until next Wednesday.
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What would be causing that cylinder to be so much richer? :o|
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AFAIK the carbs are all clean. I didn't have any problems whatsoever until I put these pipes on and changed the pilots and mains. I'm not really trying to read the plugs yet to get it set perfect or anything I'm just trying to get it to where it will run decent. Right now the only thing I'm trying to figure out is the idle to like 1/8th throttle. Once I open it up a little more than that it will clear up and run pretty good. But if I slow down and put around at all the thing runs like crap. :o|
 
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I just tested the coil on that cylinder and the book says the primary resistance should be .36-.48 ohms. It reads 0. The secondary resistance reads good. One of the wires going to that coil had quite a bit of corrosion on the one connector. I'm gonna try running it again now and see what it does.
 
The starter circuit looks good. There is slack in the cable and the tab that actuates the plunger doesn't touch the plunger until you just start to move the lever. :dunno: I wish that was it..
 
Yama49601 said:
The starter circuit looks good. There is slack in the cable and the tab that actuates the plunger doesn't touch the plunger until you just start to move the lever. :dunno: I wish that was it..
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But, does the plunger actually seat and seal off the starter circuit on the rich carb? Is the rubber intact, the seat clean, and does it seat well?
 
Ding said:
But, does the plunger actually seat and seal off the starter circuit on the rich carb? Is the rubber intact, the seat clean, and does it seat well?
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That's a good question. I'll look at it again tomorrow. Thanks for the help. I'll let you know.
 
take a small screw driver and simply try and push the choke plunger back in on the problem cylinder, if it moves in towards the carb some, even a 1/16th of an inch its open like these guys said. The choke circuits are very rich on yamaha flatslides and this will do what your describing.

If thats the case youll need to remove all the plungers and clean them.
 
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