NEW reed valve breather fits all Commandos? (2017)

NEW PRODUCT RELEASE

This new reed valve breather fits all models of Commandos & Atlas without any machining necessary.




The 750 Commando and Atlas version screws into the original breather vent on the left side case near the cam. Simply remove the breather vent and install the new one way reed breather. If (or whenever) your lower end is apart you can remove the original rotary valve and spring because you will no longer need it.




The 850 Mk 2 version screws into the original vent at the rear of the timing chest. Just remove the old vent tube and install the new reed breather (see Mk3 elect start version at bottom).




For those who have an electronic tac (or no tac) the front tac mount version fits all 750/850 Commandos. Bolts right on with no machining but you have the option of plugging the vents in the timing chest (plugs provided). 850 owners should plug the original vent at the rear of the timing chest.




For Maney cases and Combat versions you replace the original vent at the rear case. You have the option of plugging the timing chest vents (plugs provided).


This breather uses a high quality stainless steel reed valve from the BMW twin. The reed allows positive air pressure to escape on the down stroke and then shuts to prevent air from re-entering on the upstroke. This reduces crank pressure and helps prevent oil leaks.

Go here for more details:
http://www.jsmotorsport.com/technical_r ... eather.asp


EDITED
Here's an added photo of the new reed breather on a Mk3 electric start (edit - with aftermarket starter). Remove the original vent tube and install the new breather it its place.

Re: New reed valve breather fits all Commandos

It doesn't look as if it will fit an 850 Mk3 with the starter motor in place.

jseng1 said:

This new reed valve breather fits all models of Commandos & Atlas without any machining necessary.

The 850 version screws into the original vent at the rear of the timing chest. Just remove the old vent tube and install the new reed breather.

Click to expand...

Re: New reed valve breather fits all Commandos

Thanks for bringing that up L.A.B. I forgot to post this photo of the new breather on an electric start Mk 3 (edit - with aftermarket starter). See below.

Re: New reed valve breather fits all Commandos

jseng1 said:

Thanks for bringing that up L.A.B. I forgot to post this photo of the new breather on an electric start Mk 3. See below.

Click to expand...

That's the 'dynodave' starter though, which is shorter than the standard Prestolite motor.

Re: NEW reed valve breather fits all Commandos

Re: NEW reed valve breather fits all Commandos

L.A.B.

The tube that threads into the rear case is offset on the breather so you can rotate it for more clearance where you need it (the hose barb can be changed). And the Mk3 threaded case hole has more angle to give the breather more clearance than the Mk2. I don't own a Mk3 with a prestolite starter so I sent a sample out to a friend to check the fit and he took the photo of his bike with the Dyno dave starter (me not knowing the diff). If you or anyone else on this forum wants to work with me to make sure it fits the prestolite starter (at discount or refund) - please PM me.

Jim:

In regard to fitting a reed valve to an Atlas with the timed breather, my measurements have shown no change of pressure in the sump when the reed valve is fitted in series with the timed rotating disc in place, as compared to the timed disc alone.

I modified an XS650 valve to screw into the timed port in the same way as your new valve. I replaced one of the rocker spindle cover bolts with a pressure tap to measure the pressure in the rocker box (not the sump, but good for a measurement of relative change) and found it to be negative 18 inches of water (2000 rpm & up). When I removed the XS valve and measured the pressure with only the timed disc, it was still negative 18 inches of water!

I have always believed the timed breather to be ineffective due to leak back past the rotary disc, but these results proved me wrong. I now suppose the timed breather ineffective because the porting inside the camshaft is too small. Removing the disc will not resolve that condition, nor will a better one way device improve the internal flow characteristics.

You new valve appears to be a fine piece of work and I am sure it will be effective in the right application. But, I have to pass on my experience and data, and I am skeptical that it will result in more negative pressure in the sump when applied to the timed port, even if the rotating disc is removed.

Should the cases be split, would it not be more effective to drill and tap a 1/2 - 20 port somewhere else in the cases and plug the timed port? With the magneto in place, I do not know where that somewhere else would be, but for coil ignition Atlas' one of the other sites you mention should work well.

As for me and my magneto, I think a sump plug breather is my only option.

I hope you do not feel me a nay-say-er. Good luck with your new product.

Slick

Jim, could you explain why there is a 3/8" hose or a 1/2" hose for your Combat version please?

pantah_good said:

Jim, could you explain why there is a 3/8" hose or a 1/2" hose for your Combat version please?

Click to expand...

In case someone puts the Combat location sump mounted reed breather on their 850 elect start - because the Mk3 has a 1/2" hose fitting at the oil tank. I'll edit the web page to make it more clear.

Then I'll assume one hose size doesn't work any better than the other. My other question, which I really hesitate to ask for fear of sounding smart aleck or especially ignorant, but is there an operational advantage for using your reed valve over one like Mike's XS 650 reed valve? I'm getting close to final assembly of my engine once I button up my gearbox and I haven't settled on a breather valve yet, and there is a significant price difference there.

Sorry boys and girls but for $195 I'll have to stick with my Motor Mite vacuum valve @ $5.95 I just really don't have that kind of excess cash around.
Ride On(the cheap)
Dave

I don't have any oil leakage issues. Is there any other advantage to install one on a MKIII? Thanks

The Buckeye Rider said:

Sorry boys and girls but for $195 I'll have to stick with my Motor Mite vacuum valve @ $5.95 I just really don't have that kind of excess cash around.
Ride On(the cheap)
Dave

Click to expand...

Tried one of those years ago. Found it provided a placebo effect, but little else. Oil still passing crankshaft seal, tach drive still weeping. Went to an XS reed valve. No more leaking and weeping. Don't recall exactly how much the XS valve cost, less than $20 IIRC.

Slick - I started out with the timed Atlas breather. I got rid of it and use the reed valve. The timed breather does not work the same for all RPM when under load but the reed does. The air has to pulsate and it compresses. When the RPM changes - those pulsations do not always match the timed opening of the disc. We learned this in racing and discarded the timed discs. The reed doesn't care about timing - it just senses the pulsation. The four 1/8" holes in the cam are enough because once the positive air is pumped out there isn't much pulsating air movement going on. I use the reed on at the cam vent without the timed disc. There are others who have tested and compared the reed to the timed breather - maybe they could chime in here.

Panta - The XS breather is a good one and I've used it. The problem is that it doesn't mount directly to the motor to pick up heat and in the winter the oil can get water in it and turn gummy in the reed valve. Its best to have the valve mounted directly to the motor so it stays warm and doesn't plug up. I also didn't like the way the XS breather looked - its bulky and I had to modify the tubes to work with the hoses and the angle of the XS tubes wasn't right. Its obviously a patch up and it rubbed on my frame. What I offer costs a lot more because its custom made specifically for Nortons. I went to some trouble designing it to fit the various applications and bolt on without having to drill holes in your cases (but you can go ahead and drill for the sump breather if you don't have Combat or Maney cases).

Jim NH
If you get your Norton hot and put a lot of miles on it - you will probably see some oil weeping at the joints. If not then you have an exception. The reed valve gives you an advantage in the battle for an oil tight Norton. Some people claim a HP gain.
I don't think it would amount to much.

Thanks Jim, it is a handsome part. The photo of the Combat / Maney version, is that shown mounted on a Maney case?

That's a beautiful piece of engineering, especially since it can be used on multiple models.

pantah_good said:

Thanks Jim, it is a handsome part. The photo of the Combat / Maney version, is that shown mounted on a Maney case?

Click to expand...

Yes. Its a Maney case.

Here's a vid of the blowby diff between a reed and no reed.

[video]https://youtu.be/LBqUDIYxgAA[/video]

jseng1 said:

Slick - I started out with the timed Atlas breather. I got rid of it and use the reed valve. The timed breather does not work the same for all RPM when under load but the reed does. The air has to pulsate and it compresses. When the RPM changes - those pulsations do not always match the timed opening of the disc. We learned this in racing and discarded the timed discs. The reed doesn't care about timing - it just senses the pulsation. The four 1/8" holes in the cam are enough because once the positive air is pumped out there isn't much pulsating air movement going on. There are others who have tested and compared the reed to the timed breather - maybe they could chime in here.

Click to expand...

Jim:

I can accept your explanation of the phase difference between the timed disc and the actual pressure pulse.

The point I was trying to make in my previous post, is with the timed disc in place, the reed does not improve the negative pressure in the sump, according to my measurements. I can only defer to your experience with the timed disc removed.

It would be interesting if you can provide some pressure measurements with your new reed valve on your Atlas' timed port (you once posted your rotary disc is removed). If such data shows a substantial benefit, it is a pity a complete tear down is necessary to remove the rotary disc.

Slick

Xbacksidelsider

Thanks for the compliment. I put a lot of hours into the design to make it work.

Slick

I have not compared the diff between the reed valve with the timed disc and the reed valve without the timed disc. That's another test that needs to be done. There are some simple tests that anyone can duplicate.

Loosen the oil cap. Without the reed breather the cap will bounce well off the oil tank. With the reed breather it pretty much sits still. You can also see the amount of bubbles in the video above. Pressure tests will have to be very sensitive. Just immersing the hose into the oil changes everything. Never make this test with water because it can suck water into the motor when backing off the throttle without a reed valve.

I just realized that you can use the easy to install version of the breather without taking apart your motor. Then later on when you rebuild the motor - you can move it to the lower rear sump area if you choose. You have to drill and tap some holes as shown in the tech section of my web page but all you need is two longer screws to bolt the breather to the case, a sump breather gasket and plugs for the timing case vents.