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I am writing this thread in case someone else runs across what I did. There arent a lot of threads on sumping issues in Twin Cam bikes, but it CAN be a thing. Got a buddy with a 2015 SG. Had noticed the last few fluid changes I did that the trans seemed low. After closely monitoring, we determined it was in fact sumping straight over to the primary over a period of miles. No damage done, but a solution was needed. I read a little bit on another forum about some problems with the '14 and '15 model bikes having sumping issues.
The pre-M8 primary is a little different casting than the TC one. That meant using the HD vent kit that they sell for the M8's may work, but without the "pocket" in the casting like the M8 primary has, I was skeptical. I did some shopping, and came up with some parts on Amazon that would hopefully fix the problem. Worst case scenario, we find another primary casting and try again. My solution was to run a hose with a breather kinda like venting a crankcase on an engine.
Here's my parts list besides a short piece of fuel hose. Hose and vent install
I didn't get a picture of where i drilled and tapped, but there is a good flat spot close to the starter. Maybe a little over kill, but everything is hidden behind the plastic crotch heat shield on the bike. After a 2300 mile trip no fluid transfer at all so problem solved. Again, I know not many guys have experienced sumping on the TC Rushmore bikes, but it can be a thing in rare cases. If someone else has this going on, maybe this thread will help. This bike is a little higher mileage bike, close to 80k miles. I'm sure that has something to do with this problem. Not positive, but it would make sense. Seems as though the vent is where HD has landed on a fix for sumping, and this turned out to be an easy and cheap solution with instant results.
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2015 Sumping Issue Solved
