CreekerMike
Active Member
Plugs were mocha brown, in the world of 2 stroke mx where i come from this is an ideal color. Not sure about the color for the 951 but I asume itd be similar right?
951 Fouling plugs
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Sportster-2001-951C-Stock
Well-Known Member
Mocha brown is the correct color.
Sportster-2001-951C-Stock
Well-Known Member
Then why won't so many plugs I see fire? If you can identify a fouled plug by eye then you have a gift or your definition of fouled differs from mine. Black is soot, a fouled plug doesn't ignite fuel thus will not be black as a result of being fouled, it becomes black as a result of incomplete combustion (thus insufficient heat for self-cleaning) which leads to fouling,
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Sportster-2001-951C-Stock
Well-Known Member
Really?
You can’t tell this is a fouled spark plug?
The OP said his plugs are fouled. Should be pretty easy to see.
I can't tell you it won't fire.
Sportster-2001-951C-Stock
Well-Known Member
You've never seen perfectly normal looking mocha brown plugs that won't fire? Besides, I wasn't asking you b/c I'm not interested in communicating with butt sniffers.
No I haven’t seen perfect burning plugs that won’t fire. I have seen oil fouled ones that won’t and whenever I have had a true fouled plug it has been oily and wet.
Maybe NGK can explain it better than me.
“: A spark plug is considered fouled when the insulator nose at the firing tip becomes coated with a foreign substance such as fuel, oil or carbon. ... Worn piston rings or valve seals may allow too much oil to leak into the combustion chamber, leading to oil fouling.”
And how do you know if I was or wasn’t sniffing butts?
What I am trying to get at is maybe his plugs aren’t fouled with oil, maybe he has weak spark and once they get dirty there isn’t enough energy to jump the gap.
To the OP, Can you please post some pictures of the fouled plugs.
Maybe NGK can explain it better than me.
“: A spark plug is considered fouled when the insulator nose at the firing tip becomes coated with a foreign substance such as fuel, oil or carbon. ... Worn piston rings or valve seals may allow too much oil to leak into the combustion chamber, leading to oil fouling.”
And how do you know if I was or wasn’t sniffing butts?
What I am trying to get at is maybe his plugs aren’t fouled with oil, maybe he has weak spark and once they get dirty there isn’t enough energy to jump the gap.
To the OP, Can you please post some pictures of the fouled plugs.
Sportster-2001-951C-Stock
Well-Known Member
Can't be, if it's fouled it will be black and oily. LOLROFL!
This is true on 4-stroke engines. On 2-stroke engines like we are discussing here if it is fouling from too much fuel and oil they will be black and wet.
Sportster-2001-951C-Stock
Well-Known Member
I've got a whole pile of plugs in the trash can that look perfect yet won't fire. Weak spark or loss of spark is definitely a possibility, in fact it becomes difficult to fire a plug as cylinder pressure increases, for instance during a WOT blast.
Yes, we finally agree on something. Excelsior![emoji6]
Sportster-2001-951C-Stock
Well-Known Member
I haven't been confusing 2-stroke plugs with 4-stroke, that's your assumption.
Sportster-2001-951C-Stock
Well-Known Member
I guess that makes you feel warm and fuzzy.
Sportster-2001-951C-Stock
Well-Known Member
Now I see where the 4-stroke confusion came from. My definition of fouled is a plug that won't fire, for whatever reason, if it won't apply the lotion then it gets the hose. I've seen plenty of blackened plugs self-clean back to brown once combustion temps rise to normal levels.
Sometimes just going up a heat range is all that's needed to compensate for premature fouling, example is boats that troll at low speed for long periods, the plugs load up with soot faster at low combustion temps.
CreekerMike
Active Member
Miki thats what my plugs looked like, the mocha brown was in reference to the electrode color after i used brake clean and a lighter to remove and burn off all the oil ( revealing the color tjey achieved in the time it was running.Really?
You can’t tell this is a fouled spark plug?
The OP said his plugs are fouled. Should be pretty easy to see.
Sportster-2001-951C-Stock
Well-Known Member
![0509190922[1].jpg](/data/attachments/40/40482-55b88920fb1cef673b6627bc2db9b4de.jpg)
Sportster-2001-951C-Stock
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CreekerMike
Active Member
I dont think my engine has ran long enough to develope a wash pattern. When i looked in through the rave ports the pistons were still clean.
Sportster-2001-951C-Stock
Well-Known Member
Clean and shiny piston crowns beats pitted, eroded ones by a country mile, in my book. Piston wash is the single best way to judge combustion health, plug color isn't quite as reliable but still helpful.
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Ok, now we are actually getting somewhere.
So your plugs were black and oily and under the classic description oil fouled. This would be from an overly rich condition. It doesn't matter what color your plugs are after being cleaned.
At this point I would rebuild the carbs back to spec using the "Back to Stock" kits from OSD. It will include all the correct parts, check pop-off and leak down. This will give us a base point since it is the only thing you haven't tried and it can never hurt to have fresh clean carbs with new parts.
If that doesn't correct the issue then we can start getting into much less common things like weak spark but it seems to run perfectly except for WOT which is the strange thing.
I also don't like the idea of the K&N since it gives us an unknown carb setting and vacuum signal. It is possible I guess that it is restricting the air enough at WOT that the mixture gets really rich but not completely likely either.
CreekerMike
Active Member
Currently on the water, i let the ski warm up and opened up to wot, after about 2 or 3 pulls now im only able to achieve 56-5800 rpm at wot. Plugs look fine to me... guessing now i have a rave issue. Maybe my mix was just too rich....
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Plugs look normal to me. The 56-5800 is way low for that engine your RAVE valves should be open by then.
I am still leaning towards a fuel issue. See if pulling the choke a little gets the RPM back up to 6,900 but be prepared that you could foul the plugs again.
I am still leaning towards a fuel issue. See if pulling the choke a little gets the RPM back up to 6,900 but be prepared that you could foul the plugs again.
CreekerMike
Active Member
Im gonna go with you on this one, i think its a fuel issue too. Any recomendations on a good rebuild kit? Link if possible?
I like the back to stock kits from OSD because they only include what you need. With the Mikuni kits there are quite a few parts that just go in my parts bag and never get used. OSD Back to OEM
I also replace the fuel strainers on mine since complete new ones are $23 and I use the WSM fuel selectors on the 951 skis without issues but not their carb parts but you can get the replacement valve with your OSD carb kits for the same price, just use the option click boxes.
I also replace the fuel strainers on mine since complete new ones are $23 and I use the WSM fuel selectors on the 951 skis without issues but not their carb parts but you can get the replacement valve with your OSD carb kits for the same price, just use the option click boxes.
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