Finally got the break in ride done on my 78 EX440 rebuild Sunday. 50 miles on the money and approximately 6.5 gallons of gas. This was 90% river/creek/road so most times I was cruising at 50mph and right around 6100rpm with a clutch set-up that is going back to stock.
I'm all stock and plugs read rich at every look. Today I pulled them and they appear pretty much oil fouled. PTO side not as bad as mag but I guess I'd expect it to burn a little hotter
I took a look (as best one can through the plug hole) at the pistons fully expecting to see a shiny dome but it's black in the middle with no build up and as it goes out from center it looks to have some build up. I can't see the edges to see true wash but is this a result of the pre-mix (50:1) plus the oil injection or do I have conflicting stories being told by the plugs vs. pistons?
PTO on the left, Mag on the right. They seem darker out in the garage when not under a camera flash.
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Any thoughts appreciated.
I'm all stock and plugs read rich at every look. Today I pulled them and they appear pretty much oil fouled. PTO side not as bad as mag but I guess I'd expect it to burn a little hotter
I took a look (as best one can through the plug hole) at the pistons fully expecting to see a shiny dome but it's black in the middle with no build up and as it goes out from center it looks to have some build up. I can't see the edges to see true wash but is this a result of the pre-mix (50:1) plus the oil injection or do I have conflicting stories being told by the plugs vs. pistons?
PTO on the left, Mag on the right. They seem darker out in the garage when not under a camera flash.
Any thoughts appreciated.
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steelydan
New member
With the way those plugs look , I would not change a thing until you run it past the pre-mix with the oil injection. Once running on just one of those not BOTH then check plug color.
wash
Once you get past the premix it should run even a little richer. Right now with injection and premix it would be running leaner than without the premix.
Once you get past the premix it should run even a little richer. Right now with injection and premix it would be running leaner than without the premix.
taylzee
New member
nysrx said:
Doesn't that depend on the type of injection. If the oil is mixed in the pump or if is injected into the case intake side of the carb? I always thought if you had a pump mix style injection system this would hold true being that some of the fuel would be displaced by oil and if it was the other style of injection it wouldn't hold true being that the amount of fuel would increase and you would become richer.
You two pretty much nailed my thoughts. Less oil=more fuel=richer, and at the same time plugs are cheap so I'm only changing one thing at at time.
I need to measure oz oil to refill vs. oz. gas to refill to get an idea on the actual burn ratio of the injection settings and may still go another tank at 100:1
Any thoughts on why the piston isn't clean or are you thinking that I'm not as rich as I think because of the premix in the equation. I can only see a diameter a little larger than a quarter so I could actually have perfect wash.. Dark brown to black & dry in the center with no buildup, but looks wet with a little buildup on the outer fringes of what I can see.
I think I need to borrow a bendalite.
I need to measure oz oil to refill vs. oz. gas to refill to get an idea on the actual burn ratio of the injection settings and may still go another tank at 100:1
Any thoughts on why the piston isn't clean or are you thinking that I'm not as rich as I think because of the premix in the equation. I can only see a diameter a little larger than a quarter so I could actually have perfect wash.. Dark brown to black & dry in the center with no buildup, but looks wet with a little buildup on the outer fringes of what I can see.
I think I need to borrow a bendalite.
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taylzee
New member
I am not familiar with your cylinders transfer ports...but I would think that you wouldn't want them cleaned off. Typically you want to see a black top with wash just at the transfers the size of a pinky nail or so. If you have more than that you are going towards the rich side. If you have less than that you are going towards the lean side. Having said that...I have seen some motors that are running synthetic and the piston wash looks real lean (no wash). But the plugs and egt say it is not.
