Leaking oil from the top of the cap...

Hi, John if you are experiencing excessive oil coming out of the crankcase breather or air filter please drain all engine oil and replace half of the same oil that comes out. Many riders are overfilling their oil system because they do not know how to properly read their oil sight glass or dipstick. The following procedure works on nearly all 4 stroke engines but to be on the safe side you should refer to your owners manual. Use your center stand if you have one.
1. Bring the engine up to operating temperature or let it idle for 5 minutes.
2. Turn off your engine and let it sit for 2 minutes, this will allow the oil from the top end to drain to the bottom.
3. Hold your bike straight up or on the center stand and wait 2 minutes for the oil in the bottom of the engine to be level in the sight glass or on the dipstick.
4. Your oil level should be between the top full mark and the bottom add oil mark.
5. Never overfill your oil system it will cause problems:
a. oil leaking out of exhaust pipes.
b. oil leaking out of breather pipe/hose.
c. oil carryover into the air cleaner.
6. Your oil site glass must "NEVER" be, completely full or empty drain or add oil as necessary.
7. Your oil dipstick must "NEVER" be over the full mark and should never be below the add mark drain or add oil as needed.
For more information about your issue and valuable "FREE" downloads that you will need for viewing or printing please click on the blue links below and for more specific information or questions at no charge please feel free to contact me at [email protected]. Good luck and have a wonderful day.
https://www.hdforums.com/forum/oil-and-oil-related-topics/1195913-oil-change-on-jiffy-stand-or-horizontal.html
http://www.mediafire.com/file/j718855sc6zdose/2002+Harley+Touring+Service+Manual.pdf
https://partsfinder.onlinemicrofiche.com/ronnies/showmodel.asp?make=hdmc
https://serviceinfo.harley-davidson.com/sip/content/document/view?id=90057&groupId=16

Could have blown a seal however before checking for that I would check the drain plug and filter seating if you changed the filter. Make sure the drain plug is not cross threaded. You can run a little low but should never over fill. Hope this will help. Most of the time if over filled you will get some smoke as well.

did you make sure to remove the old oil filter gasket before putting the new one on cause sometimes they stick on there,check your old oil filter if it has the rubber gasket on it or not,and drain 1 quart out of the oil plug if you put too much in or you will blow oil seals

For your help, there are few Car Engine oil related solved problem listed below. You can go through it.
High Oil Level on Dipstick http://whatisbyme.blogspot.in/2012/06/high-oil-level-on-dipstick.html Oil light came on and the car died? http://schematicsdiagram.blogspot.in/2012/03/oil-light-came-on-and-car-died.html How to replace Oil filler cap or breather cap? http://repairhelpcenter.blogspot.in/2012/02/how-to-replace-oil-filler-cap-or.html Oil pouring out from left front of engine? http://schematicsdiagram.blogspot.com/2012/01/oil-pouring-out-from-left-front-of.html Common Causes of Car Oil Leaks? http://schematicsdiagram.blogspot.com/2011/12/common-causes-of-car-oil-leaks.html Troubleshoot Car Oil leak? http://schematicsdiagram.blogspot.com/2011/12/troubleshoot-car-oil-leak.html 2004 Dodge Stratus: Windage Tray Problem http://howtobyme.blogspot.in/2012/07/2004-dodge-stratus-windage-tray-problem.html Toyota Highlander Sport Oil change details? http://repairhelpcenter.blogspot.com/2012/01/toyota-highlander-sport-oil-change.html Low oil pressure light on Dodge Magnum?
http://howtobyme.blogspot.com/2011/11/low-oil-pressure-light-on-dodge-magnum.html

Kia Sportage leaking oil from oil pan?
http://howtobyme.blogspot.com/2011/11/kia-sportage-leaking-oil-from-oil-pan.html
Car Turns OFF due to low oil pressure warning light?

http://schematicsdiagram.blogspot.com/2011/12/car-turns-off-due-to-low-oil-pressure.html
Toyota Corolla leaking oil from timing cover? http://technoanswers.blogspot.in/2012/02/toyota-corolla-leaking-oil-from-timing.html

Overfilling oil in engine?

http://whatisbyme.blogspot.in/2012/06/overfilling-oil-in-engine.html
2000 Dodge Ram 3500 Cummins Diesel: Oil Leak issues? http://schematicsdiagram.blogspot.in/2012/06/2000-dodge-ram-3500-cummins-diesel-oil.html-----------
These will help.Thanks.

Drain the oil and refill to correct level make sure to clean your plugs

Hi pt--
If you are certain the oil is overfilled, then yes, this should be the problem. Single cylinder engines have little tolerance for excess oil in the crankcase. Since you're at it, you may as well change the oil in the mower while you have this all apart. In order to do this safely, be sure you have disconnected the spark plug wire from the top of the plug. You do not want the mower to start while you are under it. If you are unsure, ask someone who knows how to do this safely. You should also do this on a cool mower, as gasoline could leak from the tank or carburetor and pose a burning and fire risk. That said:

To change the oil on a single-cylinder lawnmower:
1) Gather materials.
--You'll need a pan or an old bucket to catch old oil, preferably one that has enough capacity for the old oil while also allowing the mower to be positioned with all four wheels on the ground.
--Some rags.
--A set of wrenches or a socket set.
--Two fresh quarts of new motor oil of the recommended viscosity for your particular lawnmower.
2) Disconnect the spark plug from the ignition wire. You'll see a cable running to the top of the spark plug. Grab it firmly at the boot that sits atop the plug and pull firmly. If it doesn't come off easily, be sure you are pulling at the right spot.
3) Tip the mower either backwards or on its side and look underneath the cutting deck. Be careful, as gasoline may spill from the engine's tank. You should see a small square-head or hex-head plug directly below some point of the engine. That is the engine's oil-drain plug. CAUTION: You may need to rotate the cutting blade to gain access to this plug. Be aware that the blade can cut you and that if the mower starts now it can cause serious injury to yourself.
4) Locate the correctly sized wrench or socket that mates to the drain plug.
5) Using a correctly sized wrench or socket, carefully and slowly loosen the drain plug until it turns freely by hand.
6) Position your drain pan beneath the engine's drain plug.
7) Unscrew the drain plug by hand until the oil drains free. Setting the mower down on level ground with all four wheels will ensure the most old oil drains from the engine at this point. Go ahead and open the engine's oil fil cap at this time, as this also allows the oil to drain freely.
8) When the oil has stopped draining from the engine--usually a slow drip is ok--you can replace the drain plug by hand. Be sure the plug turns freely by hand--do not crossthread the plug as you will create a costly repair for yourself.
9) Tighten the plug snug--NOT samson tight--with the correct wrench or socket and wipe any oil present at the plug or surrounding area clean with a rag.
10) Remove the pan from below the mower and rest your mower on all four wheels.
11) Slowly fill the mower's cranckase to full with fresh motor oil. Often, less than a single quart is necessary. Go slow and do not overfill.
12) Tilt the mower backwards again and check for oil leaks at the plug. You may need to snug up the oil drain plug one more time before the first after-oil-change start.
13) Lower the mower, reconnect the spark plug, and start the mower. Let it run for about a minute and listen to the mower for any "bad" sounds. If you hear anything out of the ordinary, shut off the mower immediately and recheck the mower for abnormalities.
14) Shut the mower off.
15) Check the oil level. You may have to top off the fluid level again, as running the engine tends to let the fluids settle out.
16) Disconnect the spark plug once more.
17) Tilt the mower and check the drain plug one more time for leaks. Snug it up as necessary.
18) Let the mower back down to the ground and reconnect the spark plug to the ignition wire.
You should be ready to mow again. Remember to be aware of any oil drips as push the mower around after a recent change--that may indicate the plug is leaking. There is a great picture of what a mower's drain plug looks like in the link below. Just scroll down to the part where you see the picture labeled 'oil drain plug.'
http://floridagardener.com/misc/tuneup.htm
--Hope this helps, Joe.

if its the hole i think it is it should have a pipe what geos to the air intake pipe and it is proberly leaking oil cus you have overfilled it and the pressure is force it out if you have you proberly blow your head gasket if you dont drain some oil out

You should use the viscosity oil recommended in your owner's manual. Using a heavier weight oil can affect your fuel economy. If you overfilled the engine with oil, drain out a quart. Overfilling with oil will cause the oil to 'foam', and if this happens, you are not getting proper lubrication of components, which can result in damage to your engine.