Join Date: Jan 2011
Location: Calgary Alberta Canada
Couple things to consider;
1. Too much oil in the sump. The oil capacity listed in the owner's manual and the service manual is for a dry motor. I don't care how careful you are or what type of suction you use, you will never drain all the oil out of a motor during an oil change on any vehicle. There are too many nooks and crannies for the old oil to hide in, even with a warm motor and old oil flowing out like thin hot maple syrup, some will be left behind. Best guess is between 1/4 to 1/2 of a quart (I work in metric so 250-500ml). When performing a "hot oil change" never ever put the full amount of oil back into the motor. Reduce that amount show in the operator and/or service manual by 1/2 quart to begin with. Start your motor, let it warm up to circulate the new oil, ride it even for a short distance say a mile or so and come back. Shut off the bike, park it on the jiffy stand, protect your hand and remove the dipstick and check the oil level. It will most likely be in the middle or bottom third of the "OK" zone shown on the dipstick. You will not be running under the required amount of oil. It is all there. Some of it is trapped in places that cannot be accessed easily
2. Bad breather bolt system. You will have to take off your air cleaner and inspect the breather bolts, remove them to inspect them. Clean them, make sure there are no blockages. Check the o rings, on some air cleaners there are two/bolt on others only 1 per bolt. Are the o-rings in good shape? Replace any that are flattened/cut/torn. Lastly apply a vacuum or suction to the breather bolt holes in the head, DO NOT BLOW AIR INTO THEM. Only apply mild vacuum to pull out any possible "clots". This is another area where oil can and will accumulate over time in those "nooks and crannies"
3. Oil quality and multiweight. I am sure you are using a quality oil, and I am sure you are using 20W50 multiweight oil. When you change oils on the road do you use the same brand of oil, do you use the same multiweight formulation? I hate to sound like a bad Quaker State advertisement but "not all oils are the same". Many dinosaur oils have different sources from different regions and formulations can change depending on where the oil was produced. All oils must pass testing but variations in formula can all pass the same tests. Most synthetic or chemically composed oils are made in one place, for the most part, therefore consistency is usually much better. Harley Syn 3 oil as well as Harley dinosaur oils are shopped around to the lowest bidder. Suppliers can change over time for their branded oil. Again all the oils meet the testing, but do they meet or exceed? My point here is be consistent, use the same oil brand all the time. You can change the multiweight formulation depending on the season and your type of riding but choose a reputable brand and stick with it. Many of us use an aftermarket synthetic oil that we trust, Redline, Royal Purple, Amsoil to name a few. I prefer to stay away from the common big brand oils such as Mobil 1, Castrol or Quaker State. They may make great oils but they are also diversified and have several locations/refineries/chemical plants that serve regions of North America. Their oils will meet the standardized testing but their formulation between plants can and often are tweaked depending on their source oil.
In conclusion, don't over fill the engine oil sump, in fact let it run in the lower portion of the checkered area on the dip stick. Maintain your air cleaner breather bolt system. Use a consistent high quality oil that meets and exceeds the requirements of your motor and change the oil often, with smaller than suggested intervals especially when touring longer distances and having your motor run at consistent rpms for long periods of time (interstate riding). Cheap oil is cheap, good oil is more money but oil is the blood of your motor, freshen the blood more often and it will pay off with a motor that lasts longer and runs stronger. If you cheat your motor, it will cheat you out of longevity.
Those are my thoughts and practice and not necessarily the thoughts and practice of anyone else but I have never had to replace a motor in any of the vehicles in my fleet. I run GM, Dodge, Jeep, Fiat, Ford, Honda, Arctic Cat and Harley Davidson among my personal and company vehicles.