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.

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.