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  Is plug fouling cyclical or progressive?

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Author Topic:   Is plug fouling cyclical or progressive?
Salmon Tub posted 09-12-2003 08:37 PM ET (US)   Profile for Salmon Tub   Send Email to Salmon Tub  
What I mean is, If I put new plugs in, go out at trolling speed for an hour, run at cruise for an hour, then return to trolling speed for an hour, what happens to the plugs.

Now, I am talking about standard 2-stroke carburated engines with electronic ignition. Though brands and models differ, they are identicle enough in operation.

What I am wondering is, in the case above, did I foul the plugs to a certain degree during the initial trolling period, clean them a bit during cruise, then foul again during the second troll period? Or did they foul, then no change, then foul more?

I have been told that 2-strokes 'load up' and that after long periods of trolling, 'long' being an arbitrary length of time, you should not accelerate quickly, but rather slowly increase throttle until you feel the engine pick up on it's own, at which point it has sneezed and coughed out most of the recently built up soot. Is this the general concensus?

whalernut posted 09-14-2003 08:36 AM ET (US)     Profile for whalernut  Send Email to whalernut     
I use my 1975 85h.p. Johnson on my 16` Currituck to troll with, but a small kicker would be better. It had a problem with going slow enough without stalling and loading up. I tried every plug I could find and finally settled on the Denso plugs, they will troll slower and load up less and actually last longer thna the other brands. I highly reccomend them. Jack.
Salmon Tub posted 09-15-2003 07:49 PM ET (US)     Profile for Salmon Tub  Send Email to Salmon Tub     
Well, I was able to answer my own question somewhat. Plug 1 is always clean, plug 3 always black, so, I traded their places, and after a decent run with a bit of trolling, checked them. The plug in cyl. 1 which was previously from cyl. 3, and black was now completely clean. The plug in cyl. 3, which was from cyl. 1 and clean was now fouled. The electrode looked ok, but the insulator was completely black. Plug #2 was as before tan/brown insulator. The mixture is staggered a bit, and if I lean up #2 and #3 any more, you can see it in the way it idles. I can only suspect that during periods when the engine is off, accumulated oil in the block slowly drains down and makes the lower cylinder oil-rich.
jimh posted 09-23-2003 07:03 AM ET (US)     Profile for jimh  Send Email to jimh     
[Administrative post]
ShrimpBurrito posted 09-23-2003 10:42 AM ET (US)     Profile for ShrimpBurrito  Send Email to ShrimpBurrito     
I didn't think that black insulators was ever a sign of normal operating conditions. You might getting some arcing from the tip.
Salmon Tub posted 09-23-2003 05:36 PM ET (US)     Profile for Salmon Tub  Send Email to Salmon Tub     
No, black is not normal. White is not normal either from what I understand but rather a tan-honey color is best. And as close as possible to each other in color is best.
EddieS posted 09-24-2003 02:08 AM ET (US)     Profile for EddieS  Send Email to EddieS     

I still have my 1998 Nissan 90 and have had the same problem with the #3 plug.

You may want to check the coil for the #3 plug. One of the small black and white wires is routed under the CDI and wore a hole in the insulation of the wire on my motor. It was down to the copper and had a fair amount of corrosion in it. I replaced it with a new one I think it was about $60.

I have also had a leaky top seal that spun oil all over the ignitor and the charging coils causing all three coils to fail over time. I doubt this is your problem unless your top seal is leaking, my leak was seemingly small at first. In fact I thought it was caused by the previous owner spilling oil when filling the resevoir and being blown or spun by the fly wheel. You and I have discussed the intermittant problems I was having with the motor cutting out to two cylinders. I then began having charging problems with it only charging at higher rpm's and then the ignitor got worse and the intermittant problem became constant.

I tested the coils and found that both the ignitor and the charging coils were bad. The rectifier/regulator checked out fine. It is a very easy test using a digital ohm meter to check the coils and as I found out the ignitor will still funtion but will not provide enough juice for good ignition. It would probably be worth checking just for piece of mind.


Salmon Tub posted 09-24-2003 12:19 PM ET (US)     Profile for Salmon Tub  Send Email to Salmon Tub     
Good to here from you Eddie, haven't seen you here in a while. I have not checked out the coils simply because my fouling is progressive, so, in this case, it would mean that coil 2 is worse that 1, and 3 is worse than 2. I will get to the ignition side once I am satisfied with the fuel side. I recently discovered that #1 seems happiest at almost 2.25 open, despite the fact that the book calls for a max of 1.875 open. I am thinking it may be due to our gas here in Cali. being "oxygenated", thus probably causing a lean condition to start with. This is the first time I have gone over the specs. and have yet to water test, but this is the setting at which RPM's are highest, and engine does not buck. Also, this allowed me to lean up #3 down to 1.625 without any bucking as well. I suspect that oil that is coating the inside of the warm block after a run at cruise speed slowly drains through the bearings down into #3. The only way to verify would be to take the motor apart, but I am not that bored yet.

P.S., how has your season been?

EddieS posted 09-25-2003 01:27 AM ET (US)     Profile for EddieS  Send Email to EddieS     
Salmon Tub,

My season has been slow with too many trips out to the islands. Four times I have gone to the islands and up to end buoy for small grades of fish. I did have two good trips out of Bodega for limits to 25lbs before the top seal fiasco! It was necessary to replace the top seal and while I had the motor in two I replaced the bottom seal for good measure. The motor has low hours virtually no internal corrosion anywhere, shaft was perfect with no signs of overheating or scarring. The only possible causes I could come up with was possibly a faulty seal from the factory or more likely from the original owner letting it sit too long with occasional startups perhaps not long enough to get oil up to the top seal?

I am still waiting on my charging coils. It is rather a long story but there were a couple of mix ups with the local dealer that have cost me 6 weeks of waiting. First problem is they gave me a used set so badly damaged only a fool would put them in. Then they ordered the wrong ones to replace the used set they gave me. Finally the coils I need are not in Texas and had to be shipped from Japan! I am supposed to have them tomorrow, I am not holding my breath.

I am hoping to be back on the water next week.

Let me know what you find out with the carb adjustment and I will let you know how my motor runs with the new ignitor.


PS I mentioned the coil wire because the way that it is routed under the sharp corner of the CDI it is a matter of time before it wears a hole in the wire. I sanded the rough edge off the CDI and used a short piece of heat shrink to protect the wire.

jimh posted 09-26-2003 02:02 PM ET (US)     Profile for jimh  Send Email to jimh     
I bet you are talking about a Yamaha. They call the coil that powers the battery charging rectifiers the "lighting coil."

They call the coil that power the ignition high-tension system the "charging coil".

Salmon Tub posted 09-26-2003 04:44 PM ET (US)     Profile for Salmon Tub  Send Email to Salmon Tub     
No, not Yamaha, but Nissan, Jimh. But, though things like displacement, architecture and styling are different, for the most part, the systems and their functions are much the same.

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