Air compressor filter catch can $15 breather?

Nothing new, breather being possibly an over discussed topic, but thought I'd post it anyway.

Around 30 years ago I put a 2S cam in my P11 motor and lost the timed breather setup of a stock cam. The timed breather seemed to work pretty good at getting air out of the crankcase. Without that timed breather, I lost my top end power obviously, so came up with my own breather setup after about 3 different tries. It all seemed to work before I put my bike away in the corner of the garage and left it there for 30 years. I bought some other modern bikes and rode them instead of the old iron.

Well, after taking the bike out and getting it running again in May 2020, the breather worked, but it is kind of messy. Thinking I could fix it I installed a brake check valve, a small air filter (was already using one, but got a small cone shaped one), and moved the plumbing around a little. That worked, but after one short spirited 5 mile ride, it filled the brake booster check valve with oil and the air filter bubbled oil, but the motor still ran pretty good. Not good enough though, the misty oily mess was eminent. I knew about catch cans, but all the catch cans I was familiar with were for hot rod cars, and too big. Google to the rescue. The air compressor filter (catch can) that uses 1/4 inch NPT fittings is small enough to put just behind the motor in front of the transmission. It's very tight, but doesn't touch anything. What I like about it is it acts like a $300 reed valve breather (in my mind anyway). Air can escape from the crank case, but cannot be pulled back into the motor. The little catch can solved the oil contamination of the brake booster check valve and potential of oil dribbling out of the small air filter.

It is early days though, since I have not taken the bike out for a spin. I expect to see some oil in the catch can after riding it and going through at least 3rd gear. I hope it doesn't fill up in 5 miles.

Youz guys with a lot more experience than I have with Norton breather setups. What are the potential problems I could face with set of cases that were never breather/sump modified other than actually adding a hole or two to the timing side case (not subtracting holes) and running the breather out of the magneto hole into the atmosphere? I put about 5000 miles on it with my shade tree breather just blowing to the atmosphere without the check valve or catch can 30 years ago, so I'm curious about what could go wrong with what I've added.

My experience with catch cans is ...... they catch very little oil.

Unless the can is filled with a scrubber media, the oil mist simply carries thru the can and leaves with the sump gas.

If your can is filled with a scrubber media, you should orient the inflow tube so the can can drain collected oil back to the sump.

Slick

The air compressor filter is something I got at Home Depot. If I included my time to make the magneto hole cover, install the fittings in it, and buy the new air filter, the total cost would exceed $15. I lied.

I'm running with a 1 off 2 into 1 exhaust that goes just under the center of the sump drain before it comes out on the right side. I couldn't fit any of the cool sump drain reed valve solutions down there without replacing my exhaust. Not on my short list.

texasSlick said:

My experience with catch cans is ...... they catch very little oil.

Unless the can is filled with a scrubber media, the oil mist simply carries thru the can and leaves with the sump gas.

If your can is filled with a scrubber media, you should orient the inflow tube so the can can drain collected oil back to the sump.

Slick

Click to expand...

Back to the sump sounds good, but I think it might require some magic with my motor, and exhaust configuration. Probably will end up putting the pot and pan scouring media in the catch can. Have to see how it goes on the test run. The 5 micron filter in the little compressor air filter will probably clog up with oil at about 4000 RPM in second gear. Thanks

The air compressor filter I'm using is not a catch can like the majority of affordable automotive catch cans. Air can only go in one direction through the filter, not both directions like it can with many automotive catch can solutions. It has a check valve in it to prevent air from being sucked in at the wrong end. The brake booster check valve really isn't needed with this gizmo, but I left it on because the plumbing for it was already made up, and I guess I didn't think it through past wanting to see if the air compressor filter worked. I'll be removing the brake booster check valve and replacing it with an 90 degree elbow most likely if the air compressor filter holds up. The bowl is plastic unfortunately.

The little air compressor filter I used (Model # HDA70403AV) is designed to prevent oil and water from passing tough into a paint gun at up to 90psi. Granted the Norton engine is more violent than an air compressor, but I have another 3/8th inch air exit in the magneto cover plate with a very long hose on it to help reduce the violent pulses in theory. My intake valve cover is also vented with 1/4-inch vacuum hose that runs to the rear fender.

It's raining, or I'd have some real world use babble about how it works with a load on the motor.

I took the brake booster check valve off my shade tree engineered breather and now only have a small filter connected at the exit side of the compressor air filter. It works better without that brake booster restricting the air flow.



I went for a 30 mile test ride yesterday and beat on the old motor pretty good. Only had about a quarter teaspoon of oil in the catch can (cylinder with the yellow striped white label on it) when I got back. For an Atlas motor with an aftermarket cam that does not support timed crank case breathing, I doubt the CNW part does anything better other than look cool and drain the wallet.

Funny now that the interweb is so full of negative crap that could happen if you don't do this or that as defined by "Norton experts", I've been real hesitant to beat on the motor like I did when I was younger and didn't think the motor or transmission would come apart. Seems that it can still take if yesterday's romp is any indicator. Only thing I really need to pay attention to is chain stretch, and bolts rattling off.

Thanks for all the updates. After a big rebuild I’m also having fun with crankcase pressure and oil leaks. The bike runs great separate to this. I’ve got plans involving a rocker breather and one way valve from KTM big single but don’t yet have all the parts. When I make progress I’ll report back!...

Schwany said:

For an Atlas motor with an aftermarket cam that does not support timed crank case breathing, I doubt the CNW part does anything better other than look cool and drain the wallet.

Click to expand...

You doubt Jim Comstock's reed valve research? You're calling one of the most respected actual "Norton Experts" a fraud.... So does your bike have a sidecar to carry those enormous balls you have?? Do you just tape them to your forehead?? I gotta know....

o0norton0o,

LOL

That right there is crazy talk. And yes I'm calling you crazy.

I wasn't thinking about Jim Comstock period. If he designed that breather CNW sells, good for him.

Schwany said:

look cool and drain the wallet.

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Ah yes! Years before "Norton: the world's best roadholder" there was "Norton: look cool and drain the wallet" sadly, it never caught on...

SixtySeven said:

Thanks for all the updates. After a big rebuild I’m also having fun with crankcase pressure and oil leaks. The bike runs great separate to this. I’ve got plans involving a rocker breather and one way valve from KTM big single but don’t yet have all the parts. When I make progress I’ll report back!...

Click to expand...

You are welcome. You might be alone in that kind of out of the Norton box thinking, so be careful.

The air compressor filter works as a PCV breather for my Atlas turned Combat engine, and it works well. It's not that ugly, but it certainly isn't as pretty as the part JS sells or the ones CNW and NYC sells. It is not a automotive catch can like Slick is referring to. It is one of many solutions for paint guns, and it stops any liquid, water, oil what have you from getting into the air stream, and is rated over 100psi. The little air cleaner on the exit side of the filter does not get any oil mist in it, and air cannot be returned to the engine cases. It does the same thing a reed valve does with fewer internal parts, and includes a catch can. Not rocket science. Simple stuff, but not that elegant.

I did not need any crank case breather solution when using the stock P11 cam. The timed breather through the cam worked fine back in the 1970's before the internet. If any oil came out of the breather tube after the motor sat around for a long time and got some extra oil in the sump, that oil went on my chain. I wasn't monitoring it much, and thought whatever was going on was just the way it was. I did not have a rocker cover breather tube back then. It would have been interesting to use one and see what it did. My guess is probably not much. The motor was lower compression back then, and maybe a little less of an air pump. I should have saved those dished pistons, but Phil of Fair Spares America ended up with them. He could see the writing on the wall, so to speak. Me not so much.

My motor wet sumps, like many Nortons engines do, but this device has nothing to do with wet sumping. As long as I start the motor every 3 to 4 days I don't have excess oil in the sump. It clears out right away and goes back in the oil tank for recirculation like it is supposed to.

I did not do any research to determine the compressor air filter would work. I figured it would work well enough based on what it does for air tools. End of story

Farts!!

Slick was right. At best the air compressor filter is a catch can without an air tool attached to it, and not a good one without using pot scrubber media as an internal filter. The small 5 micron filter gets clogged up with oil fairly quickly. It still flows air, but not much. I have a second 3/8ths inch hose exiting the timing cover and it was doing most of the pressure relief work once the little filter got clogged up.

I fooled myself. It's no reed valve surrogate. The clogged filter made me think the air would not go back into the timing cover. I could swear that I checked whether air could enter from the exit side before I used it, but I guess not. I've drilled a few holes in the 5 micron filter and will use this thing as a catch can for the time being.

Sorry about the steaming pile of BS.