Outdoor Power Equipment (Lawn Mowers, Snow Blowers, Chain Saws and more) Discussions

    I took out the plug of Tecumseh 7hp L-head that has been sitting around since last winter.    Most of the time it was loosely covered with a tarp but at times uncovered.

    Today I took out the plug to do a compression test and the piston top had water on it.   The only way I can figure water got in there was condensation through the valves.   It rained a bit last night and this morning so moisture probably came through the valve area.  It makes an interesting case because if I looked in there after a few good days the water would probably have been gone.  I’ll bet water has been cycling in and out of the head for several months.  Not so good for cast iron bores and rings. 

   Someone might argue that they’ve looked in 50 engines and never seen water.   I’ve looked in more than 50 and the first time I’ve ever seen standing water on a piston top.  It makes a good case for drawing up the piston to the compression stroke on storage especially if your storing outside.

Good to know! I have a few machines I will likely be storing outside, covered, this summer. I will have to make sure the pistons are at (or just beyond) TDC on the compression stroke. Maybe giving the cylinders a quick blast of oil first wouldn't be a bad idea either. I realize that it's perhaps not necessary. But these are machines that I'd like to sell if we ever get some snow again, I don't want anything getting rusted up. For me, the amount of prep work would be minimal (just 2 engines), and the peace of mind would be worth it.

I would guess that piston position for storage is more important with snowblowers than mowers, given the lack of air filters? It's not just water that could get in there, but also grit from blowing dust, etc. Would it also be more important for 2-strokes than 4-strokes, given the more direct access the engine's innards (no valvetrain for the stuff to make it through first)?

This time of year is really bad for condensation.  Anything steel is still really cold. You blow some warm damp air across it and it's like water starts growing out of the part.
Yesterday I had the entire exterior of engines wet with condensation.  Literally dripping off one shroud. 

Ambient condensation on the engine's internals is wildly over-rated. 

I agree that condensation will readily accumulate on the exterior of the engine where there is a lot of exposure but very unlikely to occur with any significance on the interior.    I pulled an old Tecumseh engine from a scrap heap that had sat there for ten or more years under a bunch of junk.  I rescued it and took it into my garage to see if I could get it to run.  Took some of it apart and didn't see any rust in the cylinder nor indications of rust on rings or anything else.   If there was water on the piston top, it likely was introduced in liquid form through an opening.  Either the exhaust or the carb. 

If an engine is store in any reasonably dry shelter, it's very unlikely to have internal condensation issues unless ambient conditions are extremely moist.