NYC Norton Reed Breather Plumbing

Lineslinger · May 16, 2023

74' Mk II

Can someone either describe or post a diagram of the correct plumbing configuration of the NYC Norton breather for the crankcase?
I have a Mikes reed valve breather installed and working.

Has anyone, using the NYC breather considered/tried connecting the return line from crankcase to the oil tank via the chain oiling outlet on the oil tank?

Or...is there too much to "push" (pressure) required to send accumulated oil in the crankcase back into the oil tank?

Can one still blow the crank seal on initial start-up with a breather operational, even after a long sit with a quart or more draining down into the crankcase?
I cannot come up with a downside to having redundant breathers in place, please share your thinking? My only thought is one breather would bleed needed pressure from the other to clear crankcase?

Overthinking this is easy.
I am pretty clear on the Commando engine but enough surprises show up to keep me asking questions.

KiwiShane · May 16, 2023

Lineslinger said:
74' Mk II

Can someone either describe or post a diagram of the correct plumbing configuration of the NYC Norton breather for the crankcase?
I have a Mikes reed valve breather installed and working.

Has anyone, using the NYC breather considered/tried connecting the return line from crankcase to the oil tank via the chain oiling outlet on the oil tank?

Or...is there too much to "push" (pressure) required to send accumulated oil in the crankcase back into the oil tank?

Can one still blow the crank seal on initial start-up with a breather operational, even after a long sit with a quart or more draining down into the crankcase?
I cannot come up with a downside to having redundant breathers in place, please share your thinking? My only thought is one breather would bleed needed pressure from the other to clear crankcase?

Overthinking this is easy.
I am pretty clear on the Commando engine but enough surprises show up to keep me asking questions.

NYC crank breather install (my vocabulary version)
Remove/ un screw spigot pipe from rear of timing case and block with supplied set screw.
Remove sump plug and screw in NYC Breather plug to check for position of intended return breather pipe that runs from the NYC sump plug up the rear of the engine case (Can readjust if needed to line up perfectly)
Run return NYC hose as per "standard oil circulation" to the neck of the oil tank for unrestricted flow of oil & air.
Connect a hose to oil tank breather outlet to a small air filter or both as I did down to front sprocket.
Depending on what breather filter you use...

Fast Eddie · May 16, 2023

The crank case mounted breather works on ‘pulses’. This is why it works best with the breathing holes, that link the crank case chamber to the timing chest, plugged (although they do work fine without doing this).

By having a second external breather in place, even with a Reed valve, you’ll likely reduce the pulses, so as counter intuitive as it may sound, it’ll reduce breathing efficiency.

It really is best to remove the old one and just use the crankcase mounted breather.

ILLF8ED · May 16, 2023

The NYC breather does not work on ‘72-‘73 750 cases then, correct?

KiwiShane · May 16, 2023

ILLF8ED said:
The NYC breather does not work on ‘72-‘73 750 cases then, correct?

COPY N PASTE FROM NYC NORTON
The NYC Norton Reed Valve Breather effectively creates a negative pressure situation in your motor which can eliminate leaks and boost performance using a highly efficient double-petal reed. Originally designed by Norton guru Jim Comstock, NYC Norton manufactures and sells this beautifully fabricated component exclusively. Fits all Norton Twins (Commando/Atlas/Dominator/P11) that have a large sump screen on the bottom of the motor, and installs in minutes with no permanent modifications necessary. Kit contains breather, blanking plug, proper oil lines, stainless hose clamps, copper crush washer, and full instructions. Screw it in, plumb it up, and breathe!

Greatly reduces leaks
Fits in minutes
Complete kit and instructions
(Note: Certain Commandos built on or before 1971 utilize a crossover frame tube under the motor which can, on occasion, prevent installation of this breather. Please email info@nycnorton.com if you are unsure of compatibility)

nopdog · May 16, 2023

All other breathers must be blanked off.
As told to me by NYC not that long ago.

NorCat · May 17, 2023

On Mk3 model does the timing cover need to be open to plug any holes or just plugging the existing breathing exit tube at the rear of the cilinders is enough to take full advantage of this unique bottom crankcase breather.

Will i be able to start the motorcycle wetsumped after giving a couple of kicks to empty the crankcase a little without doing any bad thing to the seals?

Regards

Fast Eddie · May 17, 2023

NorCat said:
On Mk3 model does the timing cover need to be open to plug any holes or just plugging the existing breathing exit tube at the rear of the cilinders is enough to take full advantage of this unique bottom crankcase breather.

Will i be able to start the motorcycle wetsumped after giving a couple of kicks to empty the crankcase a little without doing any bad thing to the seals?

Regards

As already mentioned, they are designed to work by plugging those connecting holes. But they do seem to work fine without doing that.

I started mine once (920cc) with a very wet sump (by accident) with an E start and there were no issues at all.

Not sure I’d recommend doing that all the time, but it’s nice to know that it can do it if you forget etc.

possm · May 17, 2023

Why is it that necessary- "All other breathers must be blanked off" why can you not use an inline PCV valve [inline oneway valve] my thoughts shouldn't two one-way vents better than one?

kommando · May 17, 2023

ILLF8ED said:
The NYC breather does not work on ‘72-‘73 750 cases then, correct?

72 73 cases do not have the large sump plug so no way to fit a NYC breather, you can fit a XS650 reed type breather using the 72 73 rear crankcase outlet, the closer to the outlet the better so other reed type breathers with inlet and outlets at 180 degrees will allow that.

KiwiShane · May 17, 2023

This crank case reed valve breather will bolt straight up to a 72 Commando engine.
cNw / Comstock Engineering

B+Bogus · May 17, 2023

Jim Schmidt also does a '72 fitment reed valve breather, as well as the sump plug type - including a variant to fit the crossover tube frame.

One way case reed valve breather

Eliminates positive case pressure and oil leaks. Easy installation with no modifications or machining necessary. Fits 750 left side case cam breather vent, MK2 850 timing case…

jsmotorsport.com

Sump reed valve breather

Replace your sump plug with this one way reed valve breather to reduce oil leaks and pump out excess wet sump oil on start up. Fits all Norton Twins with a large screened sump plug.

jsmotorsport.com

Great to have so many options.

kommando · May 17, 2023

Yamaha WR125X inline reed valve (called an EGR valve).

Deets55 · May 17, 2023

It is my understanding that if the reed valve is installed on the timing case you do not want to blank off the holes leading from the crankcase into the timing chest. If either the sump or back of the engine case reed valve is installed it is recommended that the holes between the timing and crank be plugged. In both situations it seems that drilling a 1/4" hole near the oil pump between the crankcase and timing chest is also recommeneded. That is to lower the oil level in the timing chest.
Somewhere on the forum there is a detailed photograph.

MichaelD · May 17, 2023

B+Bogus said:
Jim Schmidt also does a '72 fitment reed valve breather, as well as the sump plug type - including a variant to fit the crossover tube frame.

One way case reed valve breather

Eliminates positive case pressure and oil leaks. Easy installation with no modifications or machining necessary. Fits 750 left side case cam breather vent, MK2 850 timing case…

jsmotorsport.com

Sump reed valve breather

Replace your sump plug with this one way reed valve breather to reduce oil leaks and pump out excess wet sump oil on start up. Fits all Norton Twins with a large screened sump plug.

jsmotorsport.com

Great to have so many options.

And Jim does aversion that will fit 1970 bikes with the frame crossmember directly under the sump plug. I've just fitted one to my 1970.

Lineslinger · May 17, 2023

Fast Eddie said:
The crank case mounted breather works on ‘pulses’. This is why it works best with the breathing holes, that link the crank case chamber to the timing chest, plugged (although they do work fine without doing this).

By having a second external breather in place, even with a Reed valve, you’ll likely reduce the pulses, so as counter intuitive as it may sound, it’ll reduce breathing efficiency.

It really is best to remove the old one and just use the crankcase mounted breather.

I suspected this in my own roundabout way of thinking this through...and thanks for your input.

Lineslinger · May 17, 2023

KiwiShane said:
NYC crank breather install (my vocabulary version)
Remove/ un screw spigot pipe from rear of timing case and block with supplied set screw.
Remove sump plug and screw in NYC Breather plug to check for position of intended return breather pipe that runs from the NYC sump plug up the rear of the engine case (Can readjust if needed to line up perfectly)
Run return NYC hose as per "standard oil circulation" to the neck of the oil tank for unrestricted flow of oil & air.
Connect a hose to oil tank breather outlet to a small air filter or both as I did down to front sprocket.
Depending on what breather filter you use...

Good stuff Shane...thank you.

Lineslinger · May 17, 2023

Thank you all for taking the time to share your insight.

The Mike's XS I have in place is working just fine, no issues.
I was just looking for a solution to draining the sump after the bike has had a long period of sitting.
That's why I was interested in the NYC Nrtn. plug/valve. And also because I continue to get creakier as the years pass and I grow less and less excited about crawling around on the floor and pulling the sump plug.

With the NYC sump breather installed properly, could one disconnect the plugs and crank the E. start a for a few revs to clear excess oil from the crankcase before starting?

KiwiShane · May 17, 2023

Lineslinger said:
Thank you all for taking the time to share your insight.

The Mike's XS I have in place is working just fine, no issues.
I was just looking for a solution to draining the sump after the bike has had a long period of sitting.
That's why I was interested in the NYC Nrtn. plug/valve. And also because I continue to get creakier as the years pass and I grow less and less excited about crawling around on the floor and pulling the sump plug.

With the NYC sump breather installed properly, could one disconnect the plugs and crank the E. start a for a few revs to clear excess oil from the crankcase before starting?

I run this system only and find a few slow kickover's with the oil tank top off quickly returns the oil to the tank..I would imagine a few short blips on the button will do the same...

I personally believe this breather is the best money spent for engines that can accommodate this unit...

laurentdom · Jun 13, 2023

Hi All,

I plan to re-use my current Comstock breather (not sump-type but 1972-type) on a MK3 crankcase, so I'll have the LH case to be milled and drilled accordingly. Can someone give me the dimensions and locations of the 3 holes to drill and mill (one "main", 2 threaded) ?
Thks in advance,
Laurent

NYC Norton Reed Breather Plumbing

Lineslinger

KiwiShane

Attachments

Fast Eddie

ILLF8ED

KiwiShane

nopdog

NorCat

Fast Eddie

possm

kommando

KiwiShane

Attachments

B+Bogus

One way case reed valve breather

Sump reed valve breather

kommando

Deets55

MichaelD

One way case reed valve breather

Sump reed valve breather

Lineslinger

Lineslinger

Lineslinger

KiwiShane

Attachments

laurentdom

Similar threads