What Happens If You Overfill Engine Oil in a Motorcycle?

Motorcycle Engine

Have you ever changed the oil on your motorcycle and when you checked the oil level later it was too high? Or you’ve had the bike serviced, and realized the oil level is above the full mark when you got home?

Or did you, like me, took matters into your own hands and mindlessly poured in too much oil before going on a trip? We all know that riding a motorcycle with too little oil can be ravaging (can cause serious engine failure), but how bad can too much oil be for your motorcycle?

Back in 2019, I overfilled my bike just before heading for a road trip. I had changed my oil many times before but this time I just wasn’t paying attention (The excitement of a road trip, I suppose).

It was all hunky-dory at first until 20 minutes later; there were massive amounts of white smoke behind me as the excess oil started burning off. I had to take my motorcycle back home, change the oil and filter again, clean the carb, clean the airbox and filter, replace the breather tube, and of course, reschedule my trip.

Too much oil in a motorcycle engine can be disastrous. Read on to find out how too much of a good thing can be a bad thing.

What does the extra engine oil do?

Putting too much oil can be quite bad for your engine.

If the oil level is way too high the excess oil will gargle into the airbox. Don’t worry, sucking oil into the airbox is not the end of the world. You may notice oil dripping out your airbox and some of this oil may be sucked back into the air intake. 

This oil will end up in the combustion chamber where it will be burned and might ruin your spark plug. You may notice blue/white smoke from your exhaust if this is happening. The oil may also clog your air filter if it is completely saturated and cause a lot of pressure due to the restricted airflow. 

If you add too much, the crankshaft which normally spins just above the oil level can dip into the oil and whip it into froth (much like an egg beater) leading the oil to lose its viscosity.

Foaming of the oil may cause the oil pressure to drop which in turn leads to a lot of heat being generated. Once that happens the oil galleries could be starved of oil. And even though you have too much oil in your engine, the engine could seize for the same reasons as too little oil in it.

Depending on the design of your bike, oil could also drip on your clutch and cause it to slip.

However, none of these consequences are too serious if attended to quickly.

What to Do if You Overfilled Your Bike with Oil

Keep calm and don’t panic.

You’ve got a couple of options:

My go-to option is to simply unscrew the drain plug for a second and bleed off the excess oil. This is a messy business since you have to unscrew the drain plug enough for the oil to seep out, but not all the way. It will flow over your hands, tools, and other paraphernalia, so be ready. 

Tip: Use this option only if you have not run your engine until hot. You might burn yourself!

If you’ve run the engine for more than a few minutes with the excess oil, and the oil that comes out when you drain it is foamy or has lots of bubbles, your crankshaft may have started to whip the oil. In that case, drain all the oil and replace it with fresh oil. You don’t want to risk running your engine with oil that has lost its lubricating properties.                                                  

You could use a syringe and a length of hose to draw oil out of the engine. You could also use the top of a spray bottle, sticking the straw end in the oil filler hole and spraying the excess out   

Inspect the air filter. If there is saturated oil, replace it with a new filter and wipe the airbox clean with a rag or paper towels. Also, take the time to remove the spark plugs to see if they have spoiled.

If your clutch is slipping because some extra oil dripped onto it, don’t panic, it should clear up on its own after a while.

Preventive Measures

Ultimately, the best solution for overfilling your oil is to avoid doing it in the first place.

You need to start by knowing how much oil goes into your engine. You can often find a figure printed on the side of the crankcase or you can definitely find it in the owner’s manual. If you want to make sure, measure the exact quantity according to the manual in a separate container.

Pro Tip: make sure you are using the oil and filter volume and not the total engine rebuild volume which is going to be more.

Regardless of the recommended volume, it is important that you check the final oil height via the dipstick or the sight glass. I always pour in a few milliliters less than the specified quantity and check the oil level first. Make sure in the owner’s manual whether your bike needs to be on the side stand or upright when reading the oil level.

As long as your oil is within the hash marks on the dipstick or between the sight glass, you’re all good. I personally like to aim for the middle but say if you’ve got an older bike that maybe burns some oil, you might as well set it towards the top but don’t sweat it. if your oil is within the upper and lower line, it is within spec.

However, once you’ve rechecked the oil level on your motorcycle again, you can add a little oil at a time until it is just right. The few extra minutes it takes to do it right will give you peace of mind.

Conclusion               

If you notice that your motorcycle engine has too much oil in it, don’t panic. Just follow the steps mentioned above to drain a little oil out. Also, take some time to check the air filter and spark plugs. If you don’t see any leaks after you’ve cleaned up the mess, stop worrying about it. Next time, make sure to hit that maximum mark exactly.