My gz125 oil window is black so cant so how full the oils level is . when i ride the bike the problem is the same when it is hot and on level ground

Hi Jack get an oil pressure test done. If its ok replace the oil pressure switch. Regards Jim...

Your dipstick should have two marks on it. The top mark is "FULL HOT" and the lower mark is "FULL COLD". Check the oil level with the bike on the side stand. My advice is to never add oil to the oil tank when the engine is cold. As long as you can see oil on the stick, ride the bike until it reaches operating temp and then add oil only when it's below the lower mark when hot. I never "top the oil off". The reason you never add oil to the tank when cold is that if the bike is not ridden for a period of time, the oil will seep by the check valve in the oil pump. It does this because the oil tank is located higher on the frame than the engine. The oil collects in the engine cases. If you "top the oil tank off", when the engine is started and it pumps the oil from the case into the tank, the tank is now overfilled. It will blow the filler cap out and oil will go everywhere making a big mess.

Good Luck
Steve

The general rule for oil sight glasses is check them with the bike on level ground and the bike held horizontally, NOT on the side stand or centre stand. It's a good idea to get a helper, especially for a heavy bike like a this one. If you can't see any oil, you don't have enough, add more until it reaches the top of the sight glass. Just make sure it's really empty. Sometimes the glass get's an oil stain over time and it can be hard to tell when it's full of clean oil. If you really aren't sure, get someone to lift the bike off the sidestand while you are watching it and you will definitely see the oil level rise up and go over the top if it's actually over full rather than not full enough.

Unless Harley has changed something, I'm not familiar with a vent tube on the left side of a Sportster. I've always seen the vent tube coming out of the cam chest on the right side of the bike. Even the transmission vent came up and over to just behind the oil tank.

On your Sportster, make sure that you're not overfilling the oil tank. There are two lines on the dipstick. When checking your oil, the top line is 'FULL HOT" and the lower line is 'FULL COLD". Keep the level between the two lines when hot. As long as you can see oil on the dipstick, ride the bike far enough to heat up the oil and then check the level.

Otherwise, trace the hose back to it's source and tell me exactly where it comes from.

Good Luck
Steve

Check oil when bike is cold...... here is the best procedure.

Ride bike (and enjoy)
Park bike on side stand, let sit for at least 10 minutes or overnight. (lets oil drain out of cooler into sump)
Put bike on center stand. Bike should be on level ground
Check oil level in window on lower LHS of engine.
Level should be anywhere inside of red circle in sight glass.
DO NOT OVERFILL let level get down to lower edge of red circle before adding oil

Good Luck!

Sounds like you've overfilled the oil. The stick has two marks on it. The top mark is 'FULL HOT" and the lower mark is 'FULL COLD". If you changed the oil filter, you add three quarts of oil. If you did not change the filter, you only put 2.7 quarts in the tank. The next time the cap blows off, as long as the oil level is above the lower mark, do not add anymore oil and see what happens. As long as the oil level is between the marks, do not add oil. Sportsters are notorious for this. People check the oil before they go riding and "top it off". Bad move. As long as the oil is between the lines when cold, ride the bike to warm it up, and then maybe add a bit if it's low. Do not bring it up to the top line even if the engine is warm. About half way is good enough.

Good Luck
steve

With the bike standing straight up, pull the dipstick. The oil level should be between the two lines. The lower line is "Full Cold" and the upper line is "Full Hot". Do not overfill.

Ride Safe
Steve

Should be 3.5 Liters / quarts with the filter change. Put in 3 liters then top up as needed to get the level to the top of the viewing window.

To check your oil, bike should be level, on it's center stand, engine should NOT be running!

Any oil viscosity between 10w30 and 20w50 will work just fine. Smaller numbers if the weather's cooler and/or you only do short rides. Bigger numbers for hot weather and longer rides.

There is a sight-glass window on the right side of your bike. It's located near the ground in the middle of the bike. Hold the bike perfectly upright and the oil level should split the sight-glass right in the middle.

either way is fine on HD do not fill to the top of the dipstick if the oil is cold as oil expands when it is hot