A genuine question, as the M8 is a totally new engine did the HD engineers miss the chance to design a single oil in / single oil out system or is the 3 hole way, better ?
Not having a go at HD , just wondering?
Oil migration between trans and primary wouldn`t be an issue then.

 

Separate drive train makes $ sense and increases ease of upgrades. It's all about making money, but if you want to upgrade your trans but not your motor, you can do so and vise versa. Considering Harley advocates using the same oil in all 3 holes, oil migration isn't really an issue, especially from trans to primary. You should check your fluid levels often anyhow.

 

I'm sure it's been discussed by Harley engineers many times over the years. Unfortunately it would look like almost every other unitized v-twin on the market and Harley's design group wouldn't go for that.

 

Personally I like the three hole design. It keeps clutch material out of the oil stream/filtering of the engine feed. It allows otheroils to be used in tranny

 

Personally, I also like the 3-hole design. In addition to keeping clutch matter out of the mail crankcase oil, it isolates the three systems from any cross-contamination. Too, it offers the ability to run different oil for different purposes, i.e. running more "transmission oriented" oil in the tranny, etc. For me, I run dino in the trans and primary, and Syn3 in the crank. YMMV.

 

Exactly!

 

The multiple hole design is also more natural.

 

I like the options of the 3 hole design too. Just tell her "you have 3 holes and 2 hands, cover the 2 you don't want me in" ..awaitng my ban now but hey, that joke survived my college football forum!

 

I don't think I want anymore small debris going thru my bearings than already is.

 

I'm not an advocate of one oil for all uses. Especially as hot as the motor gets.