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Strange black goop forming in my new Picco engine

Strange black goop forming in my new Picco engine

Old 03-25-2020, 09:34 PM
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Default Strange black goop forming in my new Picco engine

I've been running the same fuel for years (Byron's Gen2 30% nitro / 11% oil, spiked with 50mL of extra castor oil per gallon), and my engines generally develop a faint brownish-gold color on the top of the piston and the underside of the cylinder-head after a few months of use. But my new Picco P12 engine has these weird black droplets of hardened goop forming on the top of the piston. What might be causing this?

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Old 03-26-2020, 02:00 AM
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You should have cleaned the engine. It was an old model so the oil inside was also old. Take off the backplate and inspect it is just dryed up oil or rust.
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Old 03-26-2020, 03:41 AM
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I always completely disassemble new engines so I can remove burrs on the edges of sleeve ports, or loose metal shavings, or fix any other problems that might exist. Then I wash the parts and re-oil everything with after-run oil before assembly. There was no old oil left inside this engine.

I also open the engine after the first run, and I wipe the sides of the sleeve with a cotton swab to remove any chrome flakes that came loose during the first run. I check again after each of the first 5 runs, just to be sure. That's why I had the engine open and saw this black goop forming on the top of the piston.
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Old 03-26-2020, 06:23 AM
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Looks like bad Castor. How fresh is the bottle you spike your last gallon with? Which brand?
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Old 03-26-2020, 07:18 AM
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Originally Posted by Rick Vessell View Post
Looks like bad Castor. How fresh is the bottle you spike your last gallon with? Which brand?
That's my thought as well. Looks like a castor that hasn't been de-gummed or some such.
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Old 03-26-2020, 08:14 AM
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As I di mention, must be old oil from assembling. Probably from the main bearing.
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Old 03-26-2020, 01:04 PM
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I have a quart bottle of Cool Power degummed castor oil that I've been slowly using-up for years. It's pretty old, but it's been old for a while, and I haven't seen these deposits forming before. Also they're only forming in this one engine, so it must be something about the construction or configuration of this engine that's causing it.

Now that I think a bit more about what Roelof said: This is the only engine I own that has the pullstart bearing inside the crankcase. I oiled the pullstart bearing during my initial inspection, but I didn't check if there was old grease in the bearing, because all my other engines have the pullstart bearings outside the crankcase so it doesn't matter if those pullstart bearings have old grease in them. I bet there was old grease in the pullstart bearing and it's slowly dissolving and being burned in the combustion chamber. It would be a strange oversight by Picco to assemble an engine with an internal pullstart bearing that wasn't degreased prior to installation, but...oh well.
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