I have a fairly new OS .75 maybe a gallon of fuel through it...Well the other day I was running it wide open for a while (in the air) when I brought it back in i noticed the head was a brownish color by the way this is on a Super Stick 60 with a 13x6 APC prop...Do you think it overheated or is this fuel that comes from the carb and burnt on there..The engine runs perfect and idles perfect...Seems like compression is like it always has been..

Thanks

i would have to say it is burnt oil and fuel. If it got hot enough to discolor the head it would of broke down sooner then that. could be leaking a little around the muffler seeping through the gaskets a little. spewing some out of the carb. do you fly a pattern or burn holes in the sky. I know my engines have a lot more gunk on them that are in the planes that fly a lot of maneuvers. especially stall maneuvers.

I forgot to add you can touch the flat side of the head with you thumb or fingers, fly, and your print can sometimes be "browned " on the metal Probably from the oil on your skin.

I am assuming your fuel contains castor. The brownish is burned castor. It comes off easily and is normal to some extent. If it is excessive add a gasket inbetween the pipe and engine.

Kevin

nah, that seems ok as long as you are not running it over lean. Do a pinch test on the fuel line going to the engine and it should speed up when you pinch the line. Fairly normal.

I do alot of rolls, loops, invertered...Etc The fuel I am burning is that Hobby Shop Gold from Byron...

If your doing that kinda flying your not to lean. unless you are running a pumped engine. lean runs will kill a engine when you start flipping around in the sky

Try Dawn "Power Dissolver" greatest stuff I've ever found and the cost is great about $2.95 a bottle. Just spray on and wait 20 minutes, then rense off. Engine then looks like new.

Whoa, first time I heard of that. I'm going to try to get a bottle this weekend and test it. I've done the crockpot with anti-freeze cleaning method with pretty good success, but wrecked the last engine I tried. This sounds less evasive.
http://www.dawn-dish.com/en_US/powerdissolver.do

It don't seem like it's running lean, I have never dead sticked it and seems to always blow a little smoke...

Check that the glow plug is tight. It is easy to get a small leak there and it sprays oil over the head. Also, some engines spray raw fuel from the carb which ends up being baked on the head. You can tell by the pattern where the leak is from.

Yeah wonderful stuff!

All of my engines look good as new after the winter because of it, and they have a nice clean scent too!

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To the OP.

With repeated flights the head cap screws tend to get a bit loose, which lets fuel seep out. This too will bake on and leave a brownish tinge particularly if you've used castor based fuels.

As long as the engine is not running lean you should be fine, but also do tighten them up, and check all of the cap screws while you are at it.
You may be surprised at what you find. Be careful not to strip or overtighten.