ORIGINAL: MickJC
I have not heard many people supporting the use of WD40 as after run. It's a good solvent but a poor lubricant and not as effective as after-run at corrosion prevention. It is good for blowing cr@p out of buried engines.
I always use on my boat engines. Remove the glow plug, squirt some down the carb and glow plug hole, apply starter and spin it a bit. I follow this up with some light machine oil.