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Hey everyone,


I picked up a 2015 CB300F about a year and a half ago (April 2018) new from a dealership.


Since then, I have put ~5k miles on it. At around 1500 miles, I ran it hard on a couple hundred mile drive to the beach. Knowing it was a new bike, I ignorantly didn't bother checking the oil at all during the trip, and by the time I got home it essentially had no oil and the engine made a terrible sound. I had to get serviced and have some engine internals replaced. Luckily, it was covered under warranty.



During this service, I brought up the oil issue and after it was completed, the technician said he saw no signs of oil burning or leaking. Despite that, in the last few thousand miles it has continued to lose oil and I have had to constantly check the oil before going anywhere, and more often than not, having to add oil.


Now that I have a daily highway commute, I've had to start carrying a bottle of oil with me to make sure it doesn't run low. I've taken off the fairings and looked all around the engine and have not seen any oil leaks around the engine. Is there anything I can check myself, not having the ability to take any of the engine apart, to check what is causing an oil burn/leak?


What I've tried:

  • Replacing oil, filter, and gasket, one change with Honda oil, one change with Mobil 1 T4; both still lose oil
  • Checked all around the bike for a sign of oil leakage
  • Checked the air filter for cleanliness and signs of anything abnormal

Tl;dr: Bike is losing oil, technician said no signs of oil leaks or oil burn. Where is it going then??
 

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I can't give a good answer. But it sounds like oil is going somewhere.. if not on the outside, the only place left..is internal. Have you looked at the coolant for signs of oil?? It would look milky, light brown. I'd also remove and inspect the spark plug. With the amount of oil your loosing, the plug should look a gooey, black oily mess. If nothing turns up, my last thought would be to try a thicker viscosity motor oil, but that's a last resort. Better if you could pin-point and repair the problem. Good Luck
 

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I would actually try a thicker viscosity sooner than later — easy possible solution. My thought if there aren't leaks from it sitting (hot or cold) it would be burning... You don't mention anything unusual with/coming out of the tailpipe.

My '15 uses 0 oil.
 

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I can't give a good answer. But it sounds like oil is going somewhere.. if not on the outside, the only place left..is internal. Have you looked at the coolant for signs of oil?? It would look milky, light brown. I'd also remove and inspect the spark plug. With the amount of oil your loosing, the plug should look a gooey, black oily mess. If nothing turns up, my last thought would be to try a thicker viscosity motor oil, but that's a last resort. Better if you could pin-point and repair the problem. Good Luck

Sounds like a good starting point. Will either of these point towards a specific problem or more-so just point out that there is indeed an issue?


I would actually try a thicker viscosity sooner than later — easy possible solution. My thought if there aren't leaks from it sitting (hot or cold) it would be burning... You don't mention anything unusual with/coming out of the tailpipe.

My '15 uses 0 oil.

Sorry I should have been more specific about the two oils I tried. The Honda oil is 10W-30 and the Mobil 1 is 10W-40, the only other oil I've seen on the shelves is a 20W-50, and I wasn't sure if that weight would be OK for the engine.


I also have read online about the oil haze from the exhaust, but people were saying to do it with a hot engine while driving around and having an on-looker describe what they see. I haven't been able to set something like this up, but would a hot engine idling in my parking spot work to check for the haze as well?
 

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Sounds like a good starting point. Will either of these point towards a specific problem or more-so just point out that there is indeed an issue?
Oil In the coolant would point towards a cylinder/head gasket. Or less likely, a crack somewhere in one or the other, where adjoining pieces are designed to allow oil and coolant to flow. A wet, oily spark plug would point towards a gasket/crack in the heads, piston rings, or combustion chamber. And sooner than later, you'd notice a decline in engine performance. Zeke also mentioned the exhaust. If the engine is burning oil, you'd be looking for a grayish smoke. Maybe more so at idle than rev'd up? It's conceivable the engine's not burning oil in the combustion process, and is simply forcing oil into the exhaust. I hesitate to guess how much oil could accumulate in the "catalytic converter" part of the exhaust before being forced out the tailpipe still in it's liquid form. You could check for this "oil in exhaust theory", but IMO, you'd need to look and remove the exhaust header pipe from the cylinder head.
 

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how much, oil are you using, topping up? did you take it back to the tech who saw no sign of oil burning? place a towel or tissue paper towel under it whenever parked.. if its burning oil you should see exhaust smoke..
also as mentioned spark plug is often diagnostic..
what engine parts were replaced by tech?
 

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On my bike, i'm losing oil since the beginning and I need to add some during the summer. Check the arrow on the picture.
Is there where I found some drop. It's near the oil filter cap, just more to the front.
It's not all the time but after a ride I can see some oil dropping from there. I explained this to my dealership and he told me that is probably the water pump seal that have a problem and need to be replace. I'm having now more 20k miles and the dropping is stable and is not growing. The dealership told me that many others bikes have this issue. You can check if is there you are losing your oil.
 

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Oil In the coolant would point towards a cylinder/head gasket. Or less likely, a crack somewhere in one or the other, where adjoining pieces are designed to allow oil and coolant to flow. A wet, oily spark plug would point towards a gasket/crack in the heads, piston rings, or combustion chamber. And sooner than later, you'd notice a decline in engine performance. Zeke also mentioned the exhaust. If the engine is burning oil, you'd be looking for a grayish smoke. Maybe more so at idle than rev'd up? It's conceivable the engine's not burning oil in the combustion process, and is simply forcing oil into the exhaust. I hesitate to guess how much oil could accumulate in the "catalytic converter" part of the exhaust before being forced out the tailpipe still in it's liquid form. You could check for this "oil in exhaust theory", but IMO, you'd need to look and remove the exhaust header pipe from the cylinder head.

I've turned around and monitored my exhaust several times in the past few days commuting to school and back. While sitting at red lights I will check the exhaust and as far I can tell I notice nothing unusual from it.



On my bike, i'm losing oil since the beginning and I need to add some during the summer. Check the arrow on the picture.
Is there where I found some drop. It's near the oil filter cap, just more to the front.
It's not all the time but after a ride I can see some oil dropping from there. I explained this to my dealership and he told me that is probably the water pump seal that have a problem and need to be replace. I'm having now more 20k miles and the dropping is stable and is not growing. The dealership told me that many others bikes have this issue. You can check if is there you are losing your oil.

I do not see any after a ride to school to today, but as you said yours in intermittent I will keep an eye on it.


how much, oil are you using, topping up? did you take it back to the tech who saw no sign of oil burning? place a towel or tissue paper towel under it whenever parked.. if its burning oil you should see exhaust smoke..
also as mentioned spark plug is often diagnostic..
what engine parts were replaced by tech?

Losing quite a bit. Since moving in May, I changed my oil and have been topping it off when needed, and have four empty 1qt bottles. So, a lot...


Any chance it was the piston and cylinder?

I'm really not too sure. Honestly I do not think I was given any paperwork for the service at all. I will call tomorrow and see if they kept records for it.


I have not gotten a chance to remove any coolant or the spark plug yet, I am waiting until the weekend so on the off chance I mess something up I will have a couple days to fix it before stranding myself at home and not being able to get to school. I will keep you all updated when I get the chance.
 
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