Why such a dry spark plug?

[bondobill]

Engine 97 Yamaha 200 SW 2 stroke carbed. 200 hours on factory new power head.
Last winter I pulled the plugs and I noticed #1 cylinder plug looked rather dry. I took engine into my local Yamaha dealer thinking maybe that cylinder was running lean. They tested spark, oiling and everything else that they would do on a service job. They didn't think the cylinder was running lean. They recommended I run and then inspect the plug and if I felt it was running lean to rebuild that carb.
Well I ran it on a fishing trip for a weekend and then inspected the plug and looked like it was still to dry.
I ended up putting a rebuild kit in the top carb. I did it myself and followed instructions per my manual.
Yesterday I put about 2 1/2 hours on the engine out fishing. Pulled the plug on that cylinder. To me it looks too dry compared to the other plugs
The plug on the right is from #1. The plug across from it is top plug on port side

This is a photo of #1 and the plug below it


So what y'all think. Do I have a problem or am I just paranoid ?
Btw I am running semi synthetic oil in the motor and engine has new water pump and thermostats

[99yam40]

has good color to me.
not sure if wet is normal

[bondobill]

Thanks 99 for the reply
The other plugs are not really wet but they have fuel sheen to them. #1 has no sheen at all, that's why I thought maybe it was running lean.
I first noticed it last winter while out fishing.I was having problems starting the engine after it had sat for a hour or so while *****ing on my kicker.
I pulled the plugs to replace them and found the plugs on the port side bank where wet and gunked up and #1 plug was dry and was a very light tan.
This is a photo of the plugs I pulled last winter

While I figured out was going on with the port bank of plugs. It was running too cold on that side. The head cover plate gasket was bad and letting water in past the thermostat.
I ended up replacing the head gasket on the starboard side cause I could see water seeping out between the block and the head right at the #1 cylinder. My thinking was maybe the gasket was bad and letting water in that cylinder.
With the head off that cylinder looked really good along with the other cylinders on that side
When I got it all back together I did a compression test on it a couple of times and all 6 cylinders had a even 120 compression. If I was getting water in that cylinder it looks like I caught it early before it did any damage.
Since I have rebuilt the top carb ,replaced the head gasket and got the port side bank running at the temp it supposed to I have no more starting problems...hit the key now and she fires right off.
I just wonder why that plug looks dry compared to the rest of them

Thanks
Bill

[Bluefish]

Looks like water might be cleaning that plug did you check the head for warpage before reassembly

[bondobill]

I took a straight edge to the head and it appeared to not be warped
I asked my mechanic if I should have it planed, he said definitely not.
I did what he suggested and used fine sandpaper on my 6" wood planer deck and ran the head back and forth crosshatching over that surface.

So you think I might still be getting some water in that cylinder ?

I took the motor in to the Yamy dealer after I replaced the gasket and had put a couple hours of running time on the engine. They said they didn't see a problem with that #1 plug

[rodbolt17]

plug looks like it is burning water.
do a leakdown test.
you can get water in a cyl via a bad head gasket,bad head,bad ex gasket or a bad divider plate.

[bondobill]

Thanks bluefish and rod bolt for the reply.
Ok so I got my manual out and am looking at the exhaust cover section of it.
It states many times water in the power head is caused by a leaking exhaust cover gasket or plate. In their illustration it does not reference a plate. They show the exhaust outer cover, then a gasket, inner exhaust cover, then another gasket to the block. They don't show reference to a devider plate, or is that in a different local ?
So let just say I elimate there being a bad head or head gasket because I've already been there. Can I replace the exhaust gasket with out removing the power head ? And what exactly is the devider plate ?

Sorry for the questions guys but I am far from being a outboard mechanic....been pounding fenders my entire life.

Thanks
Bill

[ausnoelm]

Just because you replaced the head gasket doesn't mean it is right, as suggested, do a leak down test

[zenoahphobic]

As above probably ingress of water, the outside electrode is the clue, it has a dull smooth "rusty" finish (might wipe a little off onto a white rag). That cylinder looks OK from a fuel mixture point of view and may "pass" inspection on a four stroke engine but suspect in your two stroke where this electrode and the other parts of the plug should show a bit more oil (oil is on the thread so it probably is getting oil). On the other hand the other plugs are a tad on the rich oily side, but I would not worry. Good pictures! Get better mechanics!

[boscoe99]

Zeno, where have you been? You have been missed.

[bondobill]

Thanks for getting back ya'll
Picked up a Harbour Freight cheap ars leak down gauge resterday. Been trying to make it work.. problem is it will only read around 12 psi in the cylinder with the leak down gauge set to zero, even with. 100 psi from the compressor. This is a photo of the readings on the suspect cylinder #1. All the other cylinders read about the same.


As you can see it showed less then a 5% loss. This gauge tester ain't nothing to brag about...instruction suck...especially for a rookie that ain't ever done a leak down test.
Today I removed the leak gauge and moved the pressure gauge to where the leak gauge was previously mounted. I then Installed a plug in the hole that the pressure gauge had been mounted. I then with the hose connected to the unit turned the units regulator until it showed 100 psi on the gauge. At this point I asked for the wife's help. While I held the flywheel at TDC on each cylinderwith a cheater bar she connected the coupler from the hose running to the spark plug hole to the pressure gauge set a 100 psi.
Photo of pressure gauge set at 100 psi before hooking up to cylinder #1


Photo of gauge after around a minute or more with 100 psi applied to #1 cylinder


All the other cylinders where within a pound or 2 of this reading.
I have no idea if I'm doing the test right or not.


Bill

[zenoahphobic]

Zeno, where have you been? You have been missed.

Winter over here, had to travel to warmer places. I'm also trying to wean myself a bit off the "left field" "devil's advocate" input that I do to provoke thought.

[zenoahphobic]

Bondobill, beautiful pictures.

The problem with your first very low pressure test, is that if logically followed: an approaching zero pressure will incorrectly tell you that you have zero leakage.

So your last pictures shows 100psi, but what does the other meter read (% loss?). You have disconnected it, so all you will see for sometime is your regulator supplying a steady pressure from your (relatively large I assume) air supply telling you nothing. If you could turn it off, but stopping the air from escaping from where it came, observe the rate at which the pressure decreases. That air loss has "leaked" past your rings or your closed valves.

I worry about these (cheap) leakdown testers. So I too would question the correct way to use it, and wonder what it actually shows you. There has been previous discussion about these in the past.

We need an expert to demonstate how to use these gauges and then tell us what then constitutes an unreasonable amount of "leak" on this engine.
I.E. what "leak" requires engine restorative work to be done. Without this all you would achieve is a compression test, and if they are similar on the other cylinders, a belief all is fine!

[Bluefish]

Correct me if aim wrong but in your first post you stated you have a 2 stroke engine I think a leak down test will only work for a 4 stroke engine

[boscoe99]

Correct me if aim wrong but in your first post you stated you have a 2 stroke engine I think a leak down test will only work for a 4 stroke engine

It will work on a two stroke motor. It just won't tell you as much. Less places for air to leak out in a two stroke given the absence of intake and exhaust valves in a two stroke.