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Leaking oil at cylinder base. Will Tman Oil Pan Vent Kit help?

Started by blown alcohol, November 24, 2021, 04:36:44 PM

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blown alcohol

Twincam 110 Cylinders are leaking oil at the Orings. I think possibly due to excess crankcase pressure.
I only have 23k miles on this performance build, and have done a lot of interstate travel this year in Aug (NC to CA)
What kits are available for venting crankcase pressure? Any recommendations?
Has anyone installed Tman oil pan vent kit?
2013 CVO Ultra


Try a search on the site for "external crankcase vent".  There are many ways to do it and you can choose what suits you best.

blown alcohol

I probably going with feuling vented oil cap. Easy install and swap to another bike.

Has anyone experienced leaking cylinders at the O-rings directly related to crankcase pressure?
2013 CVO Ultra


I would suggest one that has a one way check valve of some sort.  Open breathers w/out can raise crank case pressure. 
Semper Fi

blown alcohol

thanks, another reason to go with fueling. It has an umbrella valve built in the top of dipstick.
2013 CVO Ultra


sounds like your gasket loss integrity. Pulling the heads takes pressure off the gasket, is like breaking the seal on a beer bottle. You can't reseal it without losing integrity. It might work out most of the time, but sometimes, it doesn't re-seal very well.

This seems to happen more often with performance motors. I'm sure increasing the compression doesn't help the gasket cause. Base gasket is a PIA gasket to change, by the way.

Definitely an effin-A thing to deal with. I'd say get the best gasket money can buy and button her up.

an idiot if you do, an asshole if you don't... WTF

blown alcohol

No doubt the base gasket has to be changed.
The question is will a crankcase vent help eliminate this problem in the future?
2013 CVO Ultra


So is there a base gasket or just the orings , shouldnt leak with the orings maybe something wrong with a oring or the little ones for return line on cylinder , you can add crank vents to the heads might help it will create  some negative pressure ,

R&R cycle has a vented cam plate/cover setup but no cheap is a awsome setup but prob not worth $ just to get breathing, i reallyt think need to look at why its leaking and why so much pressure if thats really the issue , 


Quote from: blown alcohol on November 27, 2021, 01:12:53 AMNo doubt the base gasket has to be changed.
The question is will a crankcase vent help eliminate this problem in the future?

No. There is another issue that you are over looking that is the real source. Going off of your posts, you seem to have made up your mind that a case vent will solve all of your problems and you are really looking for someone to agree with you.

There are literally tens of thousands of twin cam bikes out there operating without any magical case vents without this issue. Find and fix the root problem. 
Q. What is the best ___? <br />A. Whatever YOU have

No Cents

   :agree:  with Ed. I don't think your crankcase pressure is the root cause of your problem.
I vented mine to know that it is venting. I didn't go the dipstick route. I did mine this way. It has a one way check valve in it and a filter at the end.

08 FLHX my grocery getter, 124ci, wfolarry 110" heads, Burns pipe, 158/152 sae

Ohio HD

You haven't mentioned if the leak has been from day one, or started after 23k miles. Have you tested the head vents that you can't blow inwards through the port? When the motor is running, if you can reach the dip stick opening without burning your hand, run the motor RPM's up with you hand across the opening. Is there pressure there?
For your bike part needs, call Calif Phil

blown alcohol

It has Orings. It started seeping at/around 20K+ miles. Now it is a very good leak.
I was thinking the crankcase vent might help. So, crankcase pressure would have nothing to do with leaking Orings?
I started leaking more when riding to work at temps below freezing. I do not let it warm up a lot, but also never get on throttle unless warmed up. Before winter it was just a stain around bottom edge of cylinder/case
I searched and never really see people having problems with leaking Orings.
2013 CVO Ultra


Are you using cometic base gaskets ? If so they are known to leak if you use an O ring . Had the same problem myself a bunch of years ago . Removed the O rings and installed new base gaskets and the problem never came back .
2006 Super glide 107" , 2005 electra glide 124"

Ohio HD

For your bike part needs, call Calif Phil


Got ya Brian , I didnt see what displacement he was at . Just saw performance build so i figured it was bigger C.I.D.
2006 Super glide 107" , 2005 electra glide 124"

Ohio HD

I agree about the base gasket and using an o-ring though. They generally will cause a leak.  :up:
For your bike part needs, call Calif Phil


Case seam, and or drain back O-ring. When ever I remove, and reinstall cylinders, I put a small wipe of silicone from the case seam around to under the spark plug area. Never had a problem. :up:

Jim Bronson

I had the same problem with my 110 a couple of years ago. It was a very minor 'weep' and was only enough to slightly wet the area between the cylinders and in the space between the rear cylinder and the tranny cover. I tried silicone sealant, case venting and everything else mentioned above. I finally contacted my buddy, who is the shop foreman at the local dealership. He applied case sealant to the cylinder bases, and it hasn't weeped since.
Going down that long, lonesome highway. Gonna live life my way.


Check the engine case bolt on the left side right below where the jugs form the "V" and  just above the place where the case serial number is stamped.  I had mine loosen up a little and weep oil at this point a few years ago.