DK, which kit for a PM Supergas air cleaner?

 

A couple things come into play to create the mentioned 'venturi' effect that cannot be easily created in an exhaust system downstream of the cat or any other restrictive device. The sizes of the orifice from the crankcase vent must be sized (IIRC) to 50% of the downstream side of the exhaust which has to be reduced in size just downstream of the orifice to 2x's the orifice size which creates the required velocity increase of the exhaust stream to cause the 'venturi' effect. And with all due respect, it's not a 'venturi' effect but a true siphon effect similar to what we've all seen with small siphon feed paint guns and/or sand blasters.


And even if one could find a way to reduce the exhaust stream enough to cause the siphon effect, two additional problems would immediately show their ugly heads. One is the very siphon effect itself would not only vent the crankcase, it would actually siphon the oil from the crankcase until it was somewhere near empty. We all know what happens to our engines when we run them out of oil.


We don't really want a siphon effect, just a scavenging/collecting effect of the oil that is roughly atomized and pushed out of the crankcase vent. The second problem would be the amount of back pressure created upstream the orifice and what it would do to our required exhaust flow.

We all work hard to improve exhaust flow in everyway we can. This would in fact go against that very effort not to mention what it would do to the cats. Very creative thinking until those danged ol' "Laws of Physics" sneak into play. Regards, Joe.


Now if I may I'd like to ask a question regarding this fix...................


I'm reading through every post and see the info seems to relate to bigger engines but I've not seen anything relating to a fix for an 883 or a 1200 Sportster engine. I'm not real sure of what the difference is in them, but does the Sportster designed engine not have this problem of oil in the crankcase venting?

The main reason I ask is that a few weeks ago I was reading a thread of an 883 owner who had applied this fix but his bike was literally puking oil from his aftermarket filter. Unfortunately I don't remember his name or what thread it was, but maybe he'll see this and find something of help to him. Again, thanks and regards, Joe.

 

Either of the DIY Head Breather Systems at this LINK will work.

 

If an engine is running properly, and a good EBS is in place, there will be no drops of oil on the ground or in the garage.

Regarding Sportsters, they "breathe" the same way as the Twin Cams, and there is an entire line of External Breather Systems for them HERE.

I read that same thread about the sporty puking oil. It was after he had a zippers kit installed and he ended up getting it resolved. One of his heads was defective (reportedly, it did not have a drain hole drilled). It has been fixed by the dealer and he is running one of our EBS and is no longer puking any oil.

 

Thanks for that update Kevin. Glad he got it straightened out. But I thought I had read he was still having problems even after finding the non-drilled head. Hope that's not the case.


So, if I'm understanding you correctly, the Sportster motors need this same modification. I just recently bought a 'new to me' Sportster that I've wanted since about 1969-70 when I watched a TV show called "Then Came Bronson".


Well, I got married in '69 so there went my Sportster until a couple months ago. I'm still learning what I can about it and any little bit of info helps. I'll certainly be looking into some kind of vent system the minute I see any signs.


BTW............ what is a "zipper" kit?

Regards, Joe.

 

Zippers make engine up grades, I think he had upgraded his 1200 cc to 88 CI with a Zippers kit.

Yes, the Sportsters relieve crankcase pressure up thru the push rod tubes, into the rocker cases, and out breather bolts into the air cleaner, just like the Twin Cams.

This puts that hot, oily, oxygen depleted air into the combustion chambers, building up carbon deposits, sacrificing power and engine longevity.

The engine is so much happier with an External Breather System (EBS) so that only clean, oxygen rich air is going into the combustion chambers.

 

Breather by pass , keeping stock a c.
My breather element came today so I got it done, not as I had envisioned it, but close. The breather is 2 inches in diameter, which sucked. 1 1/4 would have been ideal. This caused me to carve, which I didn't want to do. After carving out the necessary clearance to allow for the bigger than I wanted element , it all went together very easy. It still was only 15 bucks. I think it will work just fine, and still is completely hidden.
My only question is, should I seal up where the hoses exit the back plate, and where the element projects thru the backplate? Or not bother.

 

You've kind of defeated the whole purpose of the mod.

 

Interior of back plate. My intention was to keep the breather element completely out of the ac, but when I got it today, I kind of got pissed that it was so big and used it anyway. I can still close it off completely from the interior, without much trouble. Kind of figured that would be best.

 

Looks like dirty air will be getting around the air cleaner and into the motor the way it is now. I would seal that up good if I were you