[Moto Fugazzi]

When I changed my primary fluid last of my 2003 Bullet, I noticed the PO had gasket sealant on the bottom of the case cover. This was obviously done due to the large ding on the cover, which wouldn't let the cover seal properly. After filing and smoothing the ding and using Hylomar sealant (apparently not enough), I still have significant leaking, which means that I'll replace the primary cover and gasket.

Anyway, since I'm replacing the cover, is there any need to vent the primary case? I would put a small vent in the cover instead of the case.
Would there be any benefits to doing this?

[Leonard]

Mine had a vent hole in the filler plug.

[greekxj]

Ya my 07 has a vented filler plug also.

[mustangdave]

same here...vent in the filler plug on my 05

[ace.cafe]

I don't really think it is necessary to vent it, but it doesn't hurt anything.

[barenekd]

The primary case is stand alone and shouldn't require venting. It's not like the unit construction Triumph and BSAs that vented the crankcase into the primary, then vented the primary case. They weren't true UCEs as all the components, gearbox, engine and primary cases, still had separate oil chambers, as opposed to the new stuff that shares the lube all around.
However, as Ace sez, it can't hurt.
Bare

[baird4444]

why??
    you're already changing the cover with the ding that is leaking....
   if it ain't broke, don't fix it - Mike

[Moto Fugazzi]

why??
    you're already changing the cover with the ding that is leaking....
   if it ain't broke, don't fix it - Mike

Well, it only takes all of 5 minutes to drill and tap it for a vent. If this helps the bike from leaking in the future, then it's worth it.
As I see it now, I thought I had the ding removed and sealed properly, but that doesn't seem to be the case. Never had Hylomar fail on me until this point.

[Moto Fugazzi]

Mine had a vent hole in the filler plug.

Does anybody have a pic of this,or know where to get one? My filler plug is just a slotted bolt on the side of the case. I also have leakage from the filler bolt, the oil level bolt as well as the bottom of the primary case. I've varied the oil level from the bare minimum to about .75 quarts. Using 20wt oil, but will probably change to ATF-F when I change the cover and gaskets.

[greekxj]

Does anybody have a pic of this,or know where to get one? My filler plug is just a slotted bolt on the side of the case. I also have leakage from the filler bolt, the oil level bolt as well as the bottom of the primary case. I've varied the oil level from the bare minimum to about .75 quarts. Using 20wt oil, but will probably change to ATF-F when I change the cover and gaskets.

I dont have a pic but it is basically a hex headed bolt(the hex head sticks out from the cover, not flush) and it has a little hole on one of the hex sides to vent. The hex is an 18mm or 19mm in size. Not sure if that plug will thread in to where yours is. CMW can get it for you but you gotta find out if the threads are the same etc. Im sure someone here will know.

[Blltrdr]

Wow what is the preoccupation for having this vent. Mine has no vent and have not had one problem. I think I would not worry about the vent. These bikes have done just fine without one for 50+ yrs. I have seen pictures of a line from the catch can hooked up to a stub on the primary. I would presume this is some kind of EPA or import regulation and I'm not even sure they ever did this to the Bullets sold in the US.

[Spitting Bull]

I would have bet money on my 350 not having any vent hole but I've just checked and there's a tiny hole through the centre of the inspection plug.  This came as a surprise!  I'm not sure that venting is necessary, though, as there's only 420 ml of oil splashing about in there and I don't see how it can build up any noticeable pressure. Mine is the 18 mm hegagon inspection plug, by the way.  I believe there are slotted ones, too, though I've never seen one.

Tom

[The Garbone]

My 95 has a slotted on and I think the 99 junker I had did also.  No vent on those.   

Honestly I think the seal on the countershaft is loose enough that any excess preasure would be released around that.  Neither of  my primary cases leak at all and they both have the factory gasket.   I would check for machining marks that can be smoothed out and check the inner primary case with a straight edge to see if its warped. 

Being an 03 is it Kick only with no tumor?  My 07 leaked from the back of the turmor and it was part of the reason I converted it to KS only.

[cyrusb]

The vent is necessary. If you have a closed vessel with oil in it, and the temp rises, it will pressurize, causing leaks. Which is why my 05 has a pinhole in its inspection plug. It's that simple. An extra benefit of that hole is it makes the bike that much lighter.

[Chasfield]

Though air turbulence around the pin hole will increase aerodynamic drag - which negates the weight saving.