Thanks for jumping in Rich with your instructions, very helpful to me and others.
I was still doing it the old fashioned way by copy and paste.
The Harley slobber... oil leak from the air filter.
- Thread starter oldscoolz
- Start date
Thanks for jumping in Rich with your instructions, very helpful to me and others.
I was still doing it the old fashioned way by copy and paste.
oldscoolz
Member
Thanks for the replies.
Jeff and Dolt think the best way to deal with slobber is to vent the breather externally. What made you guys decide to go this way instead of the standard crankcase vent back into the combustion chamber? Is there a specific advantage to venting externally that made you choose that option?
For those with harley slobber who are lookin at this thread and hopin for some information if not answers, here’s some background. Crankcase venting or breathers are passageways from the crankcase that relieve increased crankcase pressure that develops during when the motor is running. Unrelieved pressure can blow out crankcase oil seals and gaskets. The vented crankcase gases contain aerosolized motor oil. For environmental reasons, the “modern” crankcase venting system was designed to be a closed system, with the vented crankcase gases being directed back into the cylinder to be burned. On the V twin there are two crankcase vents that come out about midway up each cylinder on the right side. They open into the backplate of the air cleaner and into the filtered air chamber that feeds into the throttle body or carburetor. Older stage 1 kits (like my bike) just had an opening in backplate that let the vented gas into the chamber without directing it toward the inlet of the throttle body/carb. Newer versions of stage 1 kits often have an extension that directs the breather output directly into the throat of the throttle body/carb, as seen in this pic of HD’s SE Stage 1 kit. I assume this is a design modification to try to minimize slobber. These pics are examples of the modification of the newer kits.
When you have oil dripping from your air filter, you gotta decide if it’s a sign of something bad that needs to be checked out further, or if you can just let it go, or if there’s some fix you can do with the venting system to make the leak go away. After you’ve convinced yourself that it’s just simple slobber, there are two basic camps: internal modifiers and external modifiers. Internal modifiers change the venting system but the vented gases still go back into the combustion chamber. External modifiers disconnect the vent from the air cleaner and vent directly to the atmosphere, sometimes using a filter on the end of the vent tubing.
There’s an amazing amount of speculation and opinion about the pros and cons of these two ways of venting. I’ve heard some folks say they took the breather hoses off the aircleaner because they think that oil from the breather hose can damage the throttle body. If that’s a real problem we’d all like to know about it. It would be surprising given all the fuel injected bikes on the road with standard internal crankcase venting. You’d think with all those bikes, if it was a problem, it would be widespread and the manufacturers would have changed the design long ago to prevent throttle body damage from crankcase venting. I just haven’t seen any real evidence this is an issue.
Another common argument for external venting involves excessive carbon buildup in the cylinders from oil in the vented gases. Like the throttle body concern, it may be more of a theoretical concern, if you had ridiculously large amounts of oil entering the cylinder but I haven’t seen any evidence that it is a common problem or causes earlier topend rebuilds than motors with external crankcase venting. Again, you’d think given all the bikes with internal venting on the road, if it was a problem, it would be widespread and there’d be clear evidence to support that concern.
Another comment often made in these threads is that slobber should prompt a more detailed diagnostic evaluation. That might include a leakdown test to check cylinder pressure, or a variety of other possible tests. Some even suggest that you should check the filter element or the flap valve in the breather assembly. I take that kind of advice with a grain of salt. Here’s a pic of where the breather assembly is, item 22. And here’s a pic of the breather assembly. Man, in my world you gotta want some better reason to go after that than a little oil leakin onto your camcase cover. (Now if you have oil leakin from your crankcase, and you suspect high crankcase pressure, and you think the cause may be blocked venting, and the breather hoses are clear, that’s a different story, but you don’t get excessive breather oil and slobber with that scenario.)
My opinion is that unless you have an engine performance issue, a major new volume of oil coming from the breather, are adding oil between oil changes, or seeing evidence of burning oil by smoke in your exhaust, I wouldn’t begin a big diagnostic workup because of slobber alone. Those of you who are really meticulous and have time on your hands may want to do a cylinder leakdown test for slobber, but most of us, mmmmmm, probably not.
I’d recommend a simple approach to slobber. If your bike’s runnin right and you’ve got a little oil leak through the filter, don’t overfill your crankcase oil and then decide if you want to do anything at all about the slobber. If you do want to do something, choose either external venting or a modification of the internal venting that is your stock configuration. I could have slapped on a new and improved stage 1 kit with the backplate modification but I’m just too damn cheap and lazy to do that. Instead I chose a $10.50 modification of my internal stock venting. That said, if my mod doesn’t do the job, I may just go ahead with the external reroute. And if I do that I’ll probably put some type of filter on the end of it and check to make sure the filter doesn’t get clogged. I haven’t seen any information to tell me whether an oil-soaked filter of the types being used in this application restricts flow and compromises venting of the crankcase but my guess is that it probably doesn’t. Still tryin to keep it simple and common sense.
Jeff and Dolt think the best way to deal with slobber is to vent the breather externally. What made you guys decide to go this way instead of the standard crankcase vent back into the combustion chamber? Is there a specific advantage to venting externally that made you choose that option?
For those with harley slobber who are lookin at this thread and hopin for some information if not answers, here’s some background. Crankcase venting or breathers are passageways from the crankcase that relieve increased crankcase pressure that develops during when the motor is running. Unrelieved pressure can blow out crankcase oil seals and gaskets. The vented crankcase gases contain aerosolized motor oil. For environmental reasons, the “modern” crankcase venting system was designed to be a closed system, with the vented crankcase gases being directed back into the cylinder to be burned. On the V twin there are two crankcase vents that come out about midway up each cylinder on the right side. They open into the backplate of the air cleaner and into the filtered air chamber that feeds into the throttle body or carburetor. Older stage 1 kits (like my bike) just had an opening in backplate that let the vented gas into the chamber without directing it toward the inlet of the throttle body/carb. Newer versions of stage 1 kits often have an extension that directs the breather output directly into the throat of the throttle body/carb, as seen in this pic of HD’s SE Stage 1 kit. I assume this is a design modification to try to minimize slobber. These pics are examples of the modification of the newer kits.
When you have oil dripping from your air filter, you gotta decide if it’s a sign of something bad that needs to be checked out further, or if you can just let it go, or if there’s some fix you can do with the venting system to make the leak go away. After you’ve convinced yourself that it’s just simple slobber, there are two basic camps: internal modifiers and external modifiers. Internal modifiers change the venting system but the vented gases still go back into the combustion chamber. External modifiers disconnect the vent from the air cleaner and vent directly to the atmosphere, sometimes using a filter on the end of the vent tubing.
There’s an amazing amount of speculation and opinion about the pros and cons of these two ways of venting. I’ve heard some folks say they took the breather hoses off the aircleaner because they think that oil from the breather hose can damage the throttle body. If that’s a real problem we’d all like to know about it. It would be surprising given all the fuel injected bikes on the road with standard internal crankcase venting. You’d think with all those bikes, if it was a problem, it would be widespread and the manufacturers would have changed the design long ago to prevent throttle body damage from crankcase venting. I just haven’t seen any real evidence this is an issue.
Another common argument for external venting involves excessive carbon buildup in the cylinders from oil in the vented gases. Like the throttle body concern, it may be more of a theoretical concern, if you had ridiculously large amounts of oil entering the cylinder but I haven’t seen any evidence that it is a common problem or causes earlier topend rebuilds than motors with external crankcase venting. Again, you’d think given all the bikes with internal venting on the road, if it was a problem, it would be widespread and there’d be clear evidence to support that concern.
Another comment often made in these threads is that slobber should prompt a more detailed diagnostic evaluation. That might include a leakdown test to check cylinder pressure, or a variety of other possible tests. Some even suggest that you should check the filter element or the flap valve in the breather assembly. I take that kind of advice with a grain of salt. Here’s a pic of where the breather assembly is, item 22. And here’s a pic of the breather assembly. Man, in my world you gotta want some better reason to go after that than a little oil leakin onto your camcase cover. (Now if you have oil leakin from your crankcase, and you suspect high crankcase pressure, and you think the cause may be blocked venting, and the breather hoses are clear, that’s a different story, but you don’t get excessive breather oil and slobber with that scenario.)
My opinion is that unless you have an engine performance issue, a major new volume of oil coming from the breather, are adding oil between oil changes, or seeing evidence of burning oil by smoke in your exhaust, I wouldn’t begin a big diagnostic workup because of slobber alone. Those of you who are really meticulous and have time on your hands may want to do a cylinder leakdown test for slobber, but most of us, mmmmmm, probably not.
I’d recommend a simple approach to slobber. If your bike’s runnin right and you’ve got a little oil leak through the filter, don’t overfill your crankcase oil and then decide if you want to do anything at all about the slobber. If you do want to do something, choose either external venting or a modification of the internal venting that is your stock configuration. I could have slapped on a new and improved stage 1 kit with the backplate modification but I’m just too damn cheap and lazy to do that. Instead I chose a $10.50 modification of my internal stock venting. That said, if my mod doesn’t do the job, I may just go ahead with the external reroute. And if I do that I’ll probably put some type of filter on the end of it and check to make sure the filter doesn’t get clogged. I haven’t seen any information to tell me whether an oil-soaked filter of the types being used in this application restricts flow and compromises venting of the crankcase but my guess is that it probably doesn’t. Still tryin to keep it simple and common sense.
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Jack Klarich
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Dolt, you can now copy and paste also
dolt
Well-Known Member
Thanks to oldskoolz for the informative post on crank case venting but I think the issue is much less complicated.
The only reason the head breathers are not vented to the atmosphere from the factory is the EPA; the manufacturers have no choice. I have never heard that internal venting can damage the throttle body; just don't see that as a legitimate reason to external vent. On the other hand, excessive carbon build up, particularly on a modified motor that is likely 20-30psi higher CCP than stock can be a serious matter. As the carbon builds up, CCP increases which is harder on the starter and battery and heat soaked kick backs can result. A severe heat soaked kick back can tweak a crank. An extreme example for sure but possible in a high strung motor. It doesn't take more than a few millimeters of carbon buildup to increase compression. A stock motor has very low CCP, about 165psi and can tolerate a lot more carbon buildup than a performance motor that might have 190-195CCP. So, please consider the context on which I base my comments.
I do agree with oldskoolz regarding excessive "slobber" should be investigated to determine if the slobber is the result of poor ring seal, breathers not functioning properly, a clogged oil filter or leaking valve guide seals.
Anyone that subscribes to the theory that running oil levels lower than that specified by the manufacturer really needs to question that logic. Would you run your vehicle a quart low? I doubt it.
Oldskoolz example of the umbrella valves in the breathers is off. The isometric shows the early style breathers that come apart and were designed to "rebuild" by replacing the filter mesh and the umbrella valve. The umbrella valve can mal function and fail to seal. The photo oldskoolz attached is the later style "stamped" breather that was I introduced in the '12 model year. They can also be rebuilt but at $12/each; who would bother.
I will dig around in my archives for a photo the clearly illustrates the difference in carbon buildup on pistons when the breathers are vented internally and externally; it is dramatic. I think when oldskoolz sees the difference, he might have a different view of venting internally, but maybe not. I hope I can find the photo.
At the end of the day, it is a simple proposition, slobber or not, if one does not object to "aerosolized oil" into the combustion chamber, leave the OEM venting system as is. Aerosolized oil is a misnomer as the "mist" vented from the crankcase contains aerosolized oil, uncombusted fuel and moisture, yeah H2O. So, if one doesn't want that mist vented into the combustion chamber, vent externally. If I every broke down and purchased a new Harley, the first thing I would do would be to pay the Harley "tax" for a Stage I upgrade and externally vent the crank case breathers.
Both my bikes are vented externally and I spent just a few $$ more than oldskoolz.
The only reason the head breathers are not vented to the atmosphere from the factory is the EPA; the manufacturers have no choice. I have never heard that internal venting can damage the throttle body; just don't see that as a legitimate reason to external vent. On the other hand, excessive carbon build up, particularly on a modified motor that is likely 20-30psi higher CCP than stock can be a serious matter. As the carbon builds up, CCP increases which is harder on the starter and battery and heat soaked kick backs can result. A severe heat soaked kick back can tweak a crank. An extreme example for sure but possible in a high strung motor. It doesn't take more than a few millimeters of carbon buildup to increase compression. A stock motor has very low CCP, about 165psi and can tolerate a lot more carbon buildup than a performance motor that might have 190-195CCP. So, please consider the context on which I base my comments.
I do agree with oldskoolz regarding excessive "slobber" should be investigated to determine if the slobber is the result of poor ring seal, breathers not functioning properly, a clogged oil filter or leaking valve guide seals.
Anyone that subscribes to the theory that running oil levels lower than that specified by the manufacturer really needs to question that logic. Would you run your vehicle a quart low? I doubt it.
Oldskoolz example of the umbrella valves in the breathers is off. The isometric shows the early style breathers that come apart and were designed to "rebuild" by replacing the filter mesh and the umbrella valve. The umbrella valve can mal function and fail to seal. The photo oldskoolz attached is the later style "stamped" breather that was I introduced in the '12 model year. They can also be rebuilt but at $12/each; who would bother.
I will dig around in my archives for a photo the clearly illustrates the difference in carbon buildup on pistons when the breathers are vented internally and externally; it is dramatic. I think when oldskoolz sees the difference, he might have a different view of venting internally, but maybe not. I hope I can find the photo.
At the end of the day, it is a simple proposition, slobber or not, if one does not object to "aerosolized oil" into the combustion chamber, leave the OEM venting system as is. Aerosolized oil is a misnomer as the "mist" vented from the crankcase contains aerosolized oil, uncombusted fuel and moisture, yeah H2O. So, if one doesn't want that mist vented into the combustion chamber, vent externally. If I every broke down and purchased a new Harley, the first thing I would do would be to pay the Harley "tax" for a Stage I upgrade and externally vent the crank case breathers.
Both my bikes are vented externally and I spent just a few $$ more than oldskoolz.
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Well said dolt, I couldn't have explained why we do it better than your post.
oldskoolz, my only suggestion is remove your air cleaner open the butterfly and look inside. If yours has all the deposits/oily film on the walls of the intake then imagine all that junk that's coating the valves and pistons. In my opinion nothing good can come of that and dolt's explanation makes perfect sense.
oldskoolz, my only suggestion is remove your air cleaner open the butterfly and look inside. If yours has all the deposits/oily film on the walls of the intake then imagine all that junk that's coating the valves and pistons. In my opinion nothing good can come of that and dolt's explanation makes perfect sense.
oldscoolz
Member
As is often the case, I come here for new eyes on a problem and am rewarded. Thanks. Your comments prompted me to go down the rabbithole to try to separate fact from fiction and here’s what I’ve come to believe. After reviewing way too many “information” sources, two sources may be of interest to others.
The first is Harley Davidson’s own breather assembly patent application published in 2002 (http://www.google.com/patents/US6345613). The second is a detailed explanation and analysis of crankcase ventilation, blowby, and oil carry over by an engineer (www.106rallye.co.uk/members/dynofiend/breathersystems.pdf). Of particular interest to me was the large volume of gas vented from an engine crankcase and the complexity of closed (internal) venting systems because of pressure differentials created by nonproportional changes in volumes of blowby and air intake into the throttle body/carb at different operating speeds and engine loads.
I was surprised at just how much blowby there is. Regarding the volume of blowby gas, a first-order calculation of blowby for an 88 cc engine at 3000 rpms is ~40 liters/minute, assuming a highend estimate that blowby volume is 3% of air intake (with a range 0.5-4%). Now going down the rabbithole, I was surprised to learn that the blowby rate decreases with increasing engine speed and load (cylinder pressure). Rings tend to seal better with increasing rpms and cylinder pressure. The result is that the blowby rate (not volume) is greatest at low speed (rpm) and low load (cylinder pressure). Since blowby volume is a very small percentage of air intake volume (0.5-4%) and is directly related engine speed, the net result is that although blowby volume increases with rpms, it does so less than you’d expect. For example, instead of going from 30 to 50 liters/min when rpms increase from 1000 to 3000, it goes from 30 to say 40 because of the effect of engine speed on ring sealing efficiency. I know, egghead stuff. Don’t read it if it hurts.
Regarding the complexity of closed venting systems, ouch, now my head hurts. Suffice it to say that fixes (like the PCV valve) had to be created to ensure that the direction of flow of vented gases was maintained under different operating conditions.
A couple of consequences of this information caught my attention, and I think some of this relates to Dolt’s points. Because of the large volume of blowby, oil separation from blowby gases becomes particularly important to minimize oil carry over into the combustion chamber. The author of the second article uses a reference of 1 gm of oil per hour as the amount of oil carry over a “world class” engine would have.
By his description this is the amount of oil that would be captured if oil catch cans were connected to the two breather hoses. You might roughly interpret this as saying that if your harley slobber is less than a ml/hr, you haven’t got an unreasonable amount of oil carry over. I see a drop or two of oil on my camcase cover about every 5-10 times I ride. I also see some evidence of slobber on my rear cylinder exhaust pipe heat shield at times that is probably blown back from the air cleaner. I typically ride ~1-2 hrs at a time. Although I can’t say exactly how much oil carry over I have, I’m thinking it isn’t very much. So you might conclude from this that modifying the internal (closed) crankcase ventilation system is reasonable.
An alternative, and I think perfectly reasonable, approach would be to say that if your bike will pass inspection with an external (open) crankcase ventilation system, you should just do it. That way you keep blowby products out of the combustion chamber and everything else upstream in the carburetion system.
A couple of points made by Dolt were reinforced by my trip. Sendin blowby products to the combustion chamber is a compromise. I couldn’t find any scientific evidence of a detrimental effect of closed venting of blowby in terms of interval to ring/valve replacement, but the sniff test says if you don’t have to put those products back in the combustion chamber, just burn the clean stuff. Meaning vent to atmosphere. The second is that for a closed crankcase ventilation system, oil separation is important and the breather assembly is one of harley’s designs to accomplish that, so it should be workin properly for the stock crankcase ventilation system. A rabbithole for another time is how and when to test it.
I think I’ll just leave it at that. For those interested, I’ll provide some followup, probably this summer or fall after many different riding conditions and a few thousand miles.
The first is Harley Davidson’s own breather assembly patent application published in 2002 (http://www.google.com/patents/US6345613). The second is a detailed explanation and analysis of crankcase ventilation, blowby, and oil carry over by an engineer (www.106rallye.co.uk/members/dynofiend/breathersystems.pdf). Of particular interest to me was the large volume of gas vented from an engine crankcase and the complexity of closed (internal) venting systems because of pressure differentials created by nonproportional changes in volumes of blowby and air intake into the throttle body/carb at different operating speeds and engine loads.
I was surprised at just how much blowby there is. Regarding the volume of blowby gas, a first-order calculation of blowby for an 88 cc engine at 3000 rpms is ~40 liters/minute, assuming a highend estimate that blowby volume is 3% of air intake (with a range 0.5-4%). Now going down the rabbithole, I was surprised to learn that the blowby rate decreases with increasing engine speed and load (cylinder pressure). Rings tend to seal better with increasing rpms and cylinder pressure. The result is that the blowby rate (not volume) is greatest at low speed (rpm) and low load (cylinder pressure). Since blowby volume is a very small percentage of air intake volume (0.5-4%) and is directly related engine speed, the net result is that although blowby volume increases with rpms, it does so less than you’d expect. For example, instead of going from 30 to 50 liters/min when rpms increase from 1000 to 3000, it goes from 30 to say 40 because of the effect of engine speed on ring sealing efficiency. I know, egghead stuff. Don’t read it if it hurts.
Regarding the complexity of closed venting systems, ouch, now my head hurts. Suffice it to say that fixes (like the PCV valve) had to be created to ensure that the direction of flow of vented gases was maintained under different operating conditions.
A couple of consequences of this information caught my attention, and I think some of this relates to Dolt’s points. Because of the large volume of blowby, oil separation from blowby gases becomes particularly important to minimize oil carry over into the combustion chamber. The author of the second article uses a reference of 1 gm of oil per hour as the amount of oil carry over a “world class” engine would have.
By his description this is the amount of oil that would be captured if oil catch cans were connected to the two breather hoses. You might roughly interpret this as saying that if your harley slobber is less than a ml/hr, you haven’t got an unreasonable amount of oil carry over. I see a drop or two of oil on my camcase cover about every 5-10 times I ride. I also see some evidence of slobber on my rear cylinder exhaust pipe heat shield at times that is probably blown back from the air cleaner. I typically ride ~1-2 hrs at a time. Although I can’t say exactly how much oil carry over I have, I’m thinking it isn’t very much. So you might conclude from this that modifying the internal (closed) crankcase ventilation system is reasonable.
An alternative, and I think perfectly reasonable, approach would be to say that if your bike will pass inspection with an external (open) crankcase ventilation system, you should just do it. That way you keep blowby products out of the combustion chamber and everything else upstream in the carburetion system.
A couple of points made by Dolt were reinforced by my trip. Sendin blowby products to the combustion chamber is a compromise. I couldn’t find any scientific evidence of a detrimental effect of closed venting of blowby in terms of interval to ring/valve replacement, but the sniff test says if you don’t have to put those products back in the combustion chamber, just burn the clean stuff. Meaning vent to atmosphere. The second is that for a closed crankcase ventilation system, oil separation is important and the breather assembly is one of harley’s designs to accomplish that, so it should be workin properly for the stock crankcase ventilation system. A rabbithole for another time is how and when to test it.
I think I’ll just leave it at that. For those interested, I’ll provide some followup, probably this summer or fall after many different riding conditions and a few thousand miles.
