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Why is there oil down the side of my bike?
This is a post I made on another forum that I am copying over here for reference. Sorry about the pics of the 2 wheelers, but all the info is relevant for HD Trikes-
I regularly see the following questions being asked:
Why is my bike dripping oil from the air cleaner?
Why do I have so much blow-by (or as HD calls it, oil carryover)?
Why does the side of my bike get covered with oil mist?
To start with, it is important to understand that all internal combustion engines have a certain amount of blow-by. This is because, by design, they build crankcase pressure, and that that pressure has to have a place to vent.
On modern Harley's, this happens at the head breather bolts.
Prior to the hot oily air exiting via the head breather bolts, HD has what is called an umbrella valve. Its' job is to filter out the majority of the oil and have mostly hot air vent out the breather bolts. They do a pretty good job, and when everything is right, it is mostly air and a small amount of oil that vents out the head breather bolts.
Umbrella valves can go bad, however, the majority of time that there is excess oil venting out the breather bolts it is NOT from bad umbrella valves, it is usually something else.
Below is a list of the most common reasons for excessive blow-by, and what can be done about it.
1. The single most common reason is incorrect oil level. Every owners manual has instructions on what the correct level is.
However, here is the bottom line, straight from the HD owners manual-
"The correct oil level should register midway between the FULL and ADD marks on the dipstick.
If oil level is at or below the ADD mark, add only enough oil to bring the level to the middle of the two marks on the dipstick."
Of course, this is confusing because HD refers to the top mark as "Full" when in reality, they say in the same sentence that midway between the two marks is full. Typical.
lol
Read more on this subject at the link above.
2. Old oil is losing it's viscosity, or Incorrect viscosity for temperatures you are riding in.
In the HD Owners Manual the following chart appears-
If you are riding in temps of 60* or higher, the best viscosity, which will result in the least amount of blow-by, is straight 50 weight.
20-50 may have just as good of lubrication qualities as straight 50 weight, but IT WILL produce more blow-by at temps of 60 degrees and higher.
If you are riding in temps of 80* or higher, the best viscosity is straight 60 weight.
IT WILL produce LESS blow-by.
3.
The bike is running too hot.
The hotter the oil, the more blow-by. Modern synthetic oil starts breaking down around 300 degrees, and dino oil around 250 degrees. However, LONG before reaching those temps it gets thinner and by-passes the umbrella valves and results in more blow-by. Most will agree that the ideal oil temp is between 180-210 degrees.
4. It may not be the blow-by that is dripping oil or putting it across the side of your bike. If you have a re-useable filter, it may be over-oiled. Sometimes they come from the MFG.
over-oiled, and sometimes they are over-oiled after they are cleaned.
5. Excessive lugging of the engine will produce more blow-by.
The above are all things you can address fairly easily.
Below are more serious reasons, that can require more effort to fix-
1. Engine worn creating excessive blow-by.
(rings, valve seals, etc.)
2. Umbrella valves not functioning correctly.
3. Crank out of round (creating excessive crankcase pressure).
What you can do if getting excessive blow-by
Once you have made sure all the easy things are right, then if the bike is running fine and you don't want to delve into the more serious issues, there are a couple of things to do if you are still getting excessive blow-by.
1. If you have an EPA approved air cleaner that feeds the hot oily air into the air cleaner there are two choices.
A. Route it out to the atmosphere so it does not collect at the bottom of your air filter and then drip.
This is also better for your engine performance and engine longevity.
Gas engines run best on gasoline and cool dry air, not on gas, oil and hot air.
B. If you want to keep the EPA happy and keep routing into the air cleaner, then make sure the tubes feeding that hot oily air are well down the throat of the carb or throttle body so that it gets into the engine and not onto the air filter.
2. If you are using a traditional external breather system, then put the filter above the air cleaner, like shown in the pic below.
This is so the majority of oil will drain back into the engine instead of pooling in the filter.
Alternatively you can use the Discrete Breather System to route the hose down to a filter toward the bottom of the bike...
or to a "catch can" which will hold the oil and need periodic emptying.
Two examples of the many possibilities with the Discrete Breather System-
To learn more about the traditional hose/filter style breather go to this link-
http://www.dkcustomproducts.com/Comp...-ACI-EV-BR.htm
To learn more about the Discrete Breather System, go to this link-
http://www.dkcustomproducts.com/91-U...IN-EVO_c75.htm
3. If you are using Outlaw Breather Bolts, they came with extra filters.
You can put those extra filters into the bolts and they will help filter out excessive oil.
To learn more about Outlaw Breather Bolts, go to this link-
http://www.dkcustomproducts.com/Poli...K-ACI-ALBB.htm
A small amount of blow-by is normal.
It is NOT normal to have so much that oil is dripping or spraying the side of your bike.
Even if you ride really hard for long periods at 100 degrees, the most there should be is a very light film, not enough to run or drip.
I am sure as time goes by I will remember some other things that I should have added to this post, but this is a good start, and certainly covers the most common issues.
Kevin
Originally Posted by PIGGI
