I've been having a little trouble w/rough idle lately so I decided to finally poke around in the engine comp a little. I decided to take the oil filler cap off with the engine running to get a better listen at the valves.

Upon removing the cap found that there was quite a bit of pressure inside...steady pressure even after cap was pulled.

Just found this odd...Normal,not normal???

 

Is it pressure or pulsing in and out ? You want to be careful if it is the normal pulsing in and out caused by the pistons since it can suck in dirt from the engine area. Some pulsing is normal and that combined with the PCV valve Positive Crankcase Ventilation valve will act as a one way check valve and cause air to be pumped from the filtered air from the air filter box through the crankcase and into the intake. Constant pressure blowing out of the crank would indicate some piston ring problems or a cracked piston or maybe a bad exhaust valve seal or guide.

 

It could be the normal pulsing from the pistons moving up and down in the crank...I'm not very familiar with the normalities of these small motors. If you put a rag over the filler cap it will keep it blown up in a dome and it does purr not sputter or pop. The v8 fords I'm used to you can take the filler cap off and add oil while the engine is running...I'd be hesitant to try it with this thing...???