How often do you clean your engine?
And is it really necessary?

I clean my Torq .16 and O.S. 40 LA engine after every flight when oil is all over the engine. I uselly just blast it with denatured alcohol and wipe it down, unless its bad then i would take it off the mount and clean it... the internal parts of the engine I clean about once a month. I would say it is nessesary to clean an engine after a flight or so. Also if it's running sluggish clean the carb. Hope this helps.

I was just woundering what peoples PM is on the engines.

I do a complete wipedown of the heli after every flying session. So the external engine surface is just quickly cleaned with fantastik or 409. Internal engine cleaning? Never. I run synthetic fuel so even engines run for years are sparkling clean inside. The only time the engine internals are cleaned is after a crash to remove any possible dirt that was ingested.
If you run castor oil fuel I would recommend a thorough cleaning every 3 months if you fly a lot, 6 months for weekend pilots.
Every year the bearings and O rings are inspected.

Fritz

no cleaning, except a sluggish wipe down at the end of the day...
had a OS61 WC lying around for 8 years and back then it was flown with 0% nitro and quite some castor...
popped it in my heli and running now 20% all synthetic and you would not know if i wouldn't tell you...
have never even looked inside an engine...

I use Wildcat fuel and since it is full synthetic is does not turn your motor or muffler brown, it looks the same as it did when it was new. I usually only drain the tank and wipe down the frames. I will drop a little after run oil before I store it for the winter, but since I normally try to fly every night at my house I dont use it otherwise.