Jan 16, 2007, 03:29 PM
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Beaver Falls, PA
Joined Dec 2006
480 Posts
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unsticking an engine
A good rule of thumb is don't take an engine apart unless you really have to! The piston to cylinder or ring to cylinder fits are really critical and if you take the piston out, you basically have to breakin in the engine again, almost guaranteed to reduce compression.
That said, most eninges freeze up due to congealed oil. Put an old prop on the engine (after taking it out of the plane), then heat the engine with a heat gun, a hair dryer isn't hot enough. You are on yoour own with an open flame and a torch! Use gloves and once the engine is nice and hot Lean on the prop until it starts to move. Don't force it, just heat and lean, heat and lean. Once the engine turns, put some kind of air tool oil in it and turn it over. MARVEL MYSTERY OIL is NOT the same as MARVEL Air Tool Oil. The air tool oil will mix with the fuel and burn out when you run the engine the first ime, other solutions usually will foul the plug.
You can use heat to free up the carb also. Once the engine is COOL, you can put in some fuel and turn the engine over. If the bearings aren't rusted, you probably don't have to replace them. Once the engine is free, you can remove the rear cover so see how things look inside; you'll be able to see rust on at least the rear bearing. Be aware that you may destroy the rear cover gasket, so be prepared to replace it if you remove the rear cover.
Besides the obvious bearings, two other places for concern are the ring-piston and the wrist pin-conrod. If the ring doesn't expand it won't seal, but it will usually free up. The wristpin sometimes sticks to the rod and then it rocks in the piston, instead of the rod rocking on it.
Without total disassembly, there is not much you can do aboout these last two conditions. Just run the engine nice and rich for a couple of tanks after you have it cleaned up. Oh yes, and make sure you blow out all the little orifices in the carb!
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