ORIGINAL: 1QwkSport2.5r
You guys and your WD40....[&:] Using after run oil isn't a bad idea, but only for long term storage. If you run the engine dry and empty the fuel tank, no ARO is needed, generally. Using fuel with castor oil in it will protect your engine superbly! I put the piston at BDC so the crankcase can breathe and you're good to go. Never any rust in my engines.
Petroleum based anything in a model engine is hokum. I tried starting an engine that I used petroleum based ATF as ARO and it was the biggest PITA to get started. Never again will I use petroleum based anything for ARO.
I've been modelling for 16 years and have yet to get any carbon or ''deposits'' in an engine.
Oh yeah, Did I mention WD40 sucks?
If someone gets carbon buildup, run the mixture rich. The extra raw fuel will loosen some of it up. Though it rarely affects engine performance unless there is a lot of carbon.
I tend to agree with most of that. I havn't experienced any carbon build-up in any of my engines, and don't use after-run oil unless I am re-assembling an engine.
I do wonder about the running rich though. I would think that would tend to add carbon. In fact it may be the reason the carbon is there in the first place.
As I'm the curious sort, I looked up the chemistry of burning alchol, nitromethane, etc to see if carbon is produced during combustion. Basically, if the engine is tuned correctly, and you have a complete burn, carbon is not produced.
The equation for hydrocarbon combustion can be generalized by:
HC + O2 + N2 = H2O + CO2 + N2 (where HC is the hydrocarbon)
For example, Methanol:
2CH3OH + 3O2 → 2CO2 + 4H20
and nitro:
4CH3NO2 + 3O2 → 4CO2 + 6H2O + 2N2
so... no carbon, but yet some people find it in their engines, so what gives?
To quote from a Google result:
If there is too much fuel for the amount of oxygen present, the carbon portion of the [fuel] is unable to be oxidized into carbon dioxide and remains as free carbon molecules after the hydrogen has been stripped away. This is "soot".
I'm no Chemistry expert and feel a little uncomfortable psoting all these chemical equations, but it looks to me that by keeping your engine well tuned, you can avoid carbon build-up quite easily.
As far as cleaning, Brake Klean (keep away from plastic parts) or other solvents can help, but remember to apply lube during assembly. If you have tough deposits on the piston top (I'm thinking ancient lawnmower here), a plastic scraper (made from a toothbrush handle, etc.) or a wooden one (popsicle stick) can help. Maybe even a little Scotchbrite soaked in solvent. However that's for the piston top. I would suggest NEVER scraping or using abrasive material on the piston sides or inside the cylinder sleeve. Paper towels with a bit of applied solvent should handle those "delicate" surfaces.
Just be gentle. Patience is the name of the game. People without patience can sometimes get the urge to use a wire wheel or other motorized methods for cleaning, and that will no doubt ruin parts very quickly.
Be very careful cleaning the inside of the engine block. Last thing you want is "bits of something" to get in the bearings. I use Q-tips to wipe things inside, and then a spray cleaner to wash away the residue. Even then, I apply lube to the bearings and ensure they spin freely with no "gritty" or "sticking" feeling.
Complete cleaning of the outside of the engine is a real help in keeping debris from finding it's way inside once you start the dissasembly. I put clean paper on my workbench top to put the engine on, and change it a few times. I don't want dirt from previous projects gettng inside the engine (my workbench is rough wood, so it's hard to get it perfectly clean). White paper makes good contrast when working on the enigne.
hmmm... can't think of anything else at the moment