So, you need to check your Harley Milwaukee-Eight engine for a primary vent tube leak. This could actually put you, as a rider, in danger! Let’s break this situation down, so you can better understand what’s happening here. You see in 2017, Harley recognized there was an oil transfer issue with the Milwaukee-Eight engine. Oil migrated over from the transmission to the primary. This issue continued up to 2019 at which time Harley developed a for-purchase non-warranty kit to solve the issue by drilling a hole and venting the primary case. (see video below)
In 2020, Harley decided to address the oil transfer issue altogether. They began manufacturing all Milwaukee-Eight Harleys with the primary vent kit at the factory and that is still true for all current models. Learn everything you need to know about the Milwaukee-Oil transfer issue by listening to Episode 256 of the Law Abiding Biker Podcast. You can listen on any podcast platform. Head over to LawAbidingBiker.com/App and choose where you want to listen.
Here at Law Abiding Biker Media, Oscar has a 2021 Ultra Classic CVO and had 1,000 miles on it at the time of purchase. He was cleaning it one day when he noticed a large amount of oil build up over the top of the transmission and rear of the primary. We were all aware of the oil transfer issue and so we checked the oil levels. Both the transmission and the primary levels were fine, indicating no oil migration. We wondered if the oil was spewing out of the primary vent hose that was installed at the factory. But the oil level was correct in the primary and it was not overfilled, so we concluded that was not the issue. Some light research online in the less-than-credible Harley forums found very little information that could be of use.
It was determined that the Harley factory is not properly seating some of the primary vent tubes. This means that the rear flared portion of the vent tube that is supposed to seal on the inside of the primary was not pulled all the way through the hole and properly seated and sealed. Thus, oil is able to leak around and spew from the inside primary hole. From Harley-Davidson sources, we learned that this issue is not uncommon. The danger to all this oil spewing is that it gets all over your rear wheel drive belt and can potentially get onto your rear tire and that’s obviously a terrible thing. To check if your Milwaukee-Eight has this issue, just simply go visually inspect the top or your transmission and inside primary area for fresh oil splatter and a build-up.
SO WHAT’S THE SOLUTION YOU ASK? Well, Oscar’s bike was under warranty. With the known oil transfer issues, we stopped there and took it into the dealership, explaining what we’d observed and learned. It was quickly determined that we were correct. The issue is easily fixed with a pair of pliers by pulling on the vent tube on the inside of the primary all the way through and properly seating the tube seal. This is very easy for you to check and correct if it is an issue with your Milwaukee-Eight and we really hope this information helps.
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