Primary Vent Upgrade.

Bobby Schulz

Active Member
Guys I was just thinking about how easy it is for the factory vent to become clogged with clutch dust that mixes with the primary oil and start a pressure leak. I thought I would put up a super easy how to fix for the problem.

I have two problems with the factory style vent...
1) Its too small and easy to clog when the primary gets enough clutch dust in it. That can cause the pressure to go up and your nice clean bike to develop a oil leak when the fluid pushes past the seals/gaskets.
2) Where its located it tends to get a little bit of oil residue on the chrome in a place that is hard to clean.

What I suggest is the next time you have the primary cover removed is to do this. Install a stainless steel barbed pipe tube by drilling out and tapping the hole where the factory vent is located. Use something like this

Then running a clear plastic hose/braded hose to vent it to the atmosphere with a small screen filter.

Easy to do with simple tools, keeps the bike clean, and you can make sure that the filter is not clogged.

If you guys want I may sell a small kit that includes the stuff needed for the upgrade and would include the following.
1) Primary cover gasket.
2) Inspection cover gasket.
3) Drain plug O-ring.
4) Stainless steel barbed pipe fitting. (I may go strait,curved,or 90deg).
5) Drill bit that is the proper size for the tap.
6) Tap needed for threading the hole with a 3/8 extension fitting on the end.
7) Hose in choice of clear or braded.

What do you guys think?:loony:
 
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RRRUFF

Well-Known Member
Bobby, have you already done this and does it work? I got what I needed to do this a few months ago and just haven't taken the down time to install. I think it will be a good fix.
 

BigDogBro1

Made in the USA
What size and type thread is the current vent hole?
How does one correctly insert a 1/8" (tapered) NPT thread elbow into a tapered thread hole that I assume was tapped from the open primary side.

The taper on the thread would be in the wrong direction, unless the hole could be tapped from the trans side.
 
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Maxim_es

Active Member
Agree with BigDogBro1, wouldn't it have to be tapped from the trans side? I like the idea though since the stock breather seems kinda flaky. Maybe it's not though.
This might be a dumb question, but if this 90 degree barb fitting is installed, should it be left pointing up with the hose and screen attached. Just seems if it was pointing down that some primary fluid would make its way into it, and leak out. Or is the amount that makes its way into it a non-issue?
Thanks for any help.
 

Bobby Schulz

Active Member
Guys you bring up good questions and here are some answers.

Im not sure of the exact size of the stock one but I would say around 10/32? I plan on going up to a 1/4 or 3/8 size barbed fitting. So I know it will vent well and not get clogged.

Yes, it would have to be tapped from the trans side to make it work. A common drill will not fit in from that side to enlarge the hole so when you take off the primary cover it would be very easy to drill that side to enlage the hole plus you need to take it off anyway to remove the metal shavings.
A tap can be placed on the end of a extension to tap it from the trans side. That is how I did my own before I switched over to a Katara belt drive dry primary. Only I used the factory style button at that time. I still had leaks after a long ride and the factory style vent button would weep oil until it would clog then I would get a leak. This may even help to keep oil out of the starter by not letting pressure build until it pushes past the o-ring.

I would suggest it be pointed upward just to make it a little harder for oil residue etc to travel up the 90deg bend..the location of the vent is pretty high in the primary so it should not take in much and you will have a vent tube to take any oil residue away from the bike. Similar to a vent on a automotive transmission or rear end.
 
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RRRUFF

Well-Known Member
I have actually thought of running the vent tube down the transmission side of the primary case back and then vent it up under the seat. Once the primary heats up then the pressure should equalize with the atmosphere and any oil in the vent tube should run back into the primary. I think I will run a stainless steel braided hose for appearance though. I will cap off this line with a vent cap like you would find on 4X4 axles and such.
 

BigDogBro1

Made in the USA
Here is a remotely located breather system using a 10-32 O-ringed swivel elbow, adapter all having quick release with 5/32"OD flexible plastic tubing


 
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BigDogBro1

Made in the USA
I found this one between my two ears.

It's an assembly of actual parts I put together in Solidworks 3D CAD.

NO DRILLING...NO MESS INSTALLATION (If 10-32 is the correct thread).

The swivel elbow has a 10-32 thread with an O-ring. The fittings are quick-release type which allows the tubing to be easily pushed in and removed.
The tubing is 5/32" OD with about .1" ID, flexible and oil resistant. The venting capacity with this hose is more than enough to provide for any air expansion in the primary area as it slowly warms up.

Nobody has answered my earlier question yet on what thread type and size the BDM primary vent is. If it's a 10-32 then this setup can be screwed into the BDM vent hole and the new breather vent can be remotely located away from dirt and water clogging.

NOT RESPONSIBLE FOR TYPOS OR INACCURATE INFORMATION....USE AT YOUR OWN RISK.



 
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PHATASS

Active Member
I found this one between my two ears.

It's an assembly of actual parts I put together in Solidworks 3D CAD.

NO DRILLING...NO MESS INSTALLATION (If 10-32 is the correct thread).

The swivel elbow has a 10-32 thread with an O-ring. The fittings are quick-release type which allows the tubing to be easily pushed in and removed.
The tubing is 5/32" OD with about .1" ID, flexible and oil resistant. The venting capacity with this hose is more than enough to provide for any air expansion in the primary area as it slowly warms up.

Nobody has answered my earlier question yet on what thread type and size the BDM primary vent is. If it's a 10-32 then this setup can be screwed into the BDM vent hole and the new breather vent can be remotely located away from dirt and water clogging.

I want one!
 

Bobby Schulz

Active Member
One reason I dont think that the factory vent is adequate is that the factory hole is too small for proper venting. Again the reason I want to use a 1/4 inch or larger fitting.
You have to think that if the outside diameter is 1/4 inch then the hole going through it is much smaller. Now on the factory setup that is say 10/32 on the threaded part just think about how small that hole actually is.

I should have a few ready to go tomorrow and I will let you guys know.
 

toodie

Active Member
God damn there is some f'n brain power on this forum. Need to come up with a way to develop and harness this power. We could have a BDB Engineering CoOP of sorts. 'BDB MOTORCYCLES INC'
I'm hoping by osmosis I can learn from you guys :D

Keep it guys love this shit...even though most of it is Latin to me:up:
 

mark whitrock

Active Member
Way too much thought going into this, the vent is to allow gases to escape so pressure can't build up, if dust would ever clog up the screen on the vent and pressure would start to build the dust that clogged the screen would give before a seal or a gasket could fail,
 
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