I recently purchased a used Spurgin oil cooler from the classifieds here. I chose it because of the design and material and waited until one showed up used to try.
After sourcing new o rings (from oem, nice lady fyi) I began my install and cleaned all components prior to install. In the cooler I found a lot of milkshake slime. My engineer brain engaged and decided it's a problem waiting to be solved.
I contacted the seller and asked about his use of the cooler and bike. He told me mostly short rides with a single long run a year. THe source was easily identified, but what can be done to reduce it.
First, on bikes used for short runs remove any oil coolers. We all know water condensates in internal combustion engines and needs to be vaporized and vented (through the crankcase venting system). The days of venting to atmosphere are long gone. Occasional runs that heat the oil to over 212* may remove a huge slug of water accumulation (poor intake system) in the form of high humidity poor quality air fuel mix. Frequent oil changes should always be considered for bikes seldom run up to full operating temp.
A potential issue exists with any cooler made of steel that is looped high with inlet and outlet at the bottom. The sludge can and will settle in the cooler (temp changes encourage condensate) and should be drained and cleaned on bikes that see repeated short runs. If not, rust may result (think about the inside of steel crash-bar coolers).
Back to the crankcase venting system: with the motor running, vacuum from the intake draws cool humid air into the crankcase where engine heat condensates it out. If a motor is not regularly run to full operating temp the amount of condensate will overwhelm the desired oil composition. It's not feasible to de-humidify air entering the crankcase yet it may be possible to restrict flow into the crankcase and on the other side intercept the condensates after it leaves the crankcase and prior to the intake. This is especially an issue with bikes with increased displacement or run hard (high rpm) on short runs. The crankcase is of a fixed volume yet increased air flow due to crankcase venting introduces more moisture laden air as displacement and rpm increase.
I've just begun looking at this and want to toss the concepts introduced for comments. I'm aware that modifying the "emission controls" is illegal, so I'm not looking at those sorts of comments.
What I see is an issue a lot of hd owners are experiencing and little is being done to address the problem except advise frequent oil changes.
Personally I do not take the bike for quick runs to the store. If I don't have an hour to take the long road, I hop in the cage.

 

Suggest we start calling it Engineering since instead of Common since.

Lots of short runs / bike not getting up to operating temp long enough to burn off the condensation = frequent oil changes to avoid the problem (understanding Temp. and Humidity levels)(choice of running less expensive dino Oil and changing it often or higher price Synthetic Oil and going longer before change it). That is if they remember to change it.

I see the lack of understanding of how a 4 cycle engine functions. Of how the intake is a “system”, the exhaust is a “System”, the ignition / firing is a “System”, est. And how changes in one “System” effects all of the others.

It amazes me that people will spend a lot of $$$$$ on a HD, polish the paint and chrome off of it and not have a clue as to how it works.


Good idea about having drain on the oil cooler.

 

Also note that condensation can also build up in your tranny

 

Is the trans vented? If so a small vent could reduce most moisture intrusion there as, it seems to me, most air entering the system would be during cool down.

 

Kenney, do you have any thoughts on the sizing of the crankcase vent system? I have no idea how it is sized and if it over scavenges stock and how displacement and induction changes may affect the flow (oil in air filter housing). I wonder if the manfr's of aftermarket air cleaners take this into account when they design their intakes.

 

Any run that brings your oil up to temp will get rid of condensation. And as the air in your oil tank/gas tank/tranny cools down voila more condensation because warm air holds more moisture than cool air.

 

That was widely believed prior to being disproved in the early 1800's by Dalton.
Relative humidity is the phenomenon at work and the bearer of the problematic moisture.

 

Another possible explanation for the condensation is the brand of oil used. I had problems with my bikes back in the 70s when multi-grade oils became popular. They use a higher proportion of additives than the single grade oils and some brands were much more prone to generating that milky emulsion. Short runs is the main cause, but a change of brand of oil may also help.

 

That is a good point. I remain confident in concluding that atmospheric %rel humidity when riding together with short duration runs has more to do with condensates than the other factors. First I'm not suggesting one leaves a bike idling for an extended period of time to heat a motor. I am suggesting one plans their rides to include sufficient cruising to heat up the motor as the best means to reduce condensates.
I'm still trying to get my head around the design of the pvc scavenging system.
My gut feeling is that they are designed to over scavenge, resulting in a liberal flow of cool fresh air through the crankcase. I'm thinking a means to limit the air flow through the crankcase (and into the intake flow) is the 2nd best means to reduce condensate.
Condensate cannot be completely eliminated, and thus more frequent oil changes are needed to deal with the contaminate. Arid environments (desert, inland, even humid areas during very cold winter days) will have dry atmosphere and humid environments (coastal, monsoonal, fog, valleys, etc.) will have water laden atmosphere.
It seems this remains a very common problem and prevalent in air cooled aluminum made engines that are not run up to full operating temp.
I can see only the single variable of restricting air flow into the crankcase (if safely do-able) as the means to reduce condensates.

 

It was actually a common problem in cars, back in the 70s. The common source of oil/water emulsion was the oil bag on dry sump bikes and the steel rocker covers of overhead valve engines. In both cases on short trips the engine didn't get to full operating temperature, indeed on some cars the air flow through the grill never allowed the rocker covers to get very hot.

Both problems were associated with additives in early multi-grade oils. On my motorcycle I changed from single grade to multi-grade, got serious emulsion in the oil bag, changed oil brand and cured it. One friend cured his car by wrapping the rocker cover in old carpet! For some of us today a change of oil brand will probably solve the problem.