case reed breather

comnoz · Oct 21, 2016

Cobel said:
Hi Gents

Is this a reed valve in the picture.

It is not a reed valve. It is a check valve with a plastic disk and a spring to hold it closed.

A reed valve has much less mass so it is capable of opening and closing much faster than a disk valve. That means it will continue to operate and a higher engine speed [up to road speed or beyond]. Jim

ewgoforth · Oct 21, 2016

Why didn't the pressure equalize? Don't you have the big 850 style holes?

This seems like it would really be a problem if you put a reed valve on one of the early style engines that breathe through the end of the cam.

comnoz · Oct 21, 2016

ewgoforth said:
Why didn't the pressure equalize? Don't you have the big 850 style holes?

This seems like it would really be a problem if you put a reed valve on one of the early style engines that breathe through the end of the cam.

If you are referring to installing the valve as in my picture then the pressure does not equalize because when you install the valve you plug all the holes except for a small oil drainback hole into the crankcase. And of course the drainback hole that comes from the head that would normally be the oil supply for the timing chest.

swooshdave · Oct 21, 2016

comnoz said:
The testing I have done shows the case reed breather draws a little deeper depression than a breather attached to the timing chest. It will also continue to draw a depression to a higher RPM.

In reality the difference in leak prevention is very small.

The biggest benefit to my breather is rapid clearing of the excess oil in the cases after a wet sump condition or a long period of idling. Jim

Is this counter to your position that there are no drawbacks to the timing chest mount?

Benefits of case mount over timing case:
Slightly better draw
Allows evacuation of wet sump oil

MFB · Oct 21, 2016

ewgoforth said:
Why didn't the pressure equalize? Don't you have the big 850 style holes?

Gotta add my tuppence worth here.
Retaining these holes would render the reed valve useless in the location being discussed here. The pulses would simply bypass the valve.

The best solution is to evacuate the pressure at its source, which is what Jim's crankcase breather does.

The other well known method, adding a reed valve to the Norton timing case breather, is probably somewhat less effective but has been proven to reduce/eliminate oil leaks by those who use it.

comnoz · Oct 21, 2016

The timing chest mount breather is simply a less expensive alternative to a crankcase mounted breather -with less benefits.

The drawbacks to a breather that breathes from the timing chest is:

1. less crankcase depression -particularly as the rpm rises.

2. no wet sump oil scavenging

3. unless the timing chest reed valve is mounted directly to the engine case it will run cooler than the engine and will collect moisture. The oil water mixture will create a white cream that can plug the breather in time.

Advantages of a timing chest breather are:

1. it's almost as good at preventing oil leaks for considerably less money.

2. if it's hose mounted then it is very easy to install and also easy to remove and clean.

swooshdave said:
comnoz said:

The testing I have done shows the case reed breather draws a little deeper depression than a breather attached to the timing chest. It will also continue to draw a depression to a higher RPM.

In reality the difference in leak prevention is very small.

The biggest benefit to my breather is rapid clearing of the excess oil in the cases after a wet sump condition or a long period of idling. Jim

Click to expand...

Is this counter to your position that there are no drawbacks to the timing chest mount?

Benefits of case mount over timing case:
Slightly better draw
Allows evacuation of wet sump oil

xbacksideslider · Oct 21, 2016

I have a crankcase breather mounted to the backside of my 1973 750's crankcase. When the bike has sat a long time, I take the seat off and remove the oil tank fill cap so I can see in there; I then kick it through a few times until the breather quits squirting the wet sumped oil.

jseng1 · Oct 21, 2016

I haven't experienced the problems that Comstock mentions when mounting a reed valve inside the timing chest as he mentions at the beginning of this thread. I'm having no problems and the oil is draining from the intake spring rocker box and back to the timing chest as usual. There may have been something wrong with Comstock’s design that I don’t understand. I’ve tested the oil return with the reed valve and timing chest vented and made a video of the results.

[video]https://youtu.be/y3TZlr869Fc[/video]

But if Comstock can have problems then its possible that someone else can (even though I haven’t) and so I think I will hold off on the breather for now.

A question for you Jim Comstock. If the oil return from the head is the only lube source for the timing pinion, then why would did you block it – especially when you already plugged everything else? Failure was certain.

comnoz · Oct 21, 2016

By removing the valve cover to watch what is happening you would disable any possibility of creating a depression in the crankcase -the head communicates with the crankcase through the pushrod tubes.

So then of course the intake spring seat area would drain properly.

madass140 · Oct 21, 2016

Ahh, a breather hose off the inlet tappet cover???

jseng1 · Oct 21, 2016

comnoz said:
By removing the valve cover to watch what is happening you would disable any possibility of creating a depression in the crankcase -the head communicates with the crankcase through the pushrod tubes.

So then of course the intake spring seat area would drain properly.

Of course - that's obvious. And that's why I showed that it took approx 45 seconds for a rockerbox full of oil to drain back down to regular level and that's why I got that rocker cover off in less than 3 seconds in the vid - the oil level was already down to normal with over 40 seconds to spare. 6 minutes running would be plenty of time to fill up a rocker box with oil.

Here's another question for you Jim Comstock: If the oil wasn't draining back into the timing chest when you tried this type of setup - then how were the timing gears and pinon lubed? And why did your timing pinon seize only after you completely plugged the oil return from the head?

Dances with Shrapnel · Oct 21, 2016

comnoz said:
By removing the valve cover to watch what is happening you would disable any possibility of creating a depression in the crankcase -the head communicates with the crankcase through the pushrod tubes.

So then of course the intake spring seat area would drain properly.

Shrodinger's cat.

guest76 · Oct 21, 2016

madass140 said:
Ahh, a breather hose off the inlet tappet cover???

I mocked exactly that that up on an ES2 engine, using a lot of the research done by Rex Bunn.
The quality of the components he built was really poor, so I used two ET Performance KrankVents.
Breathing in through the bottom and out through the top into a small catch can worked superbly well.
Although, obviously no ability to evacuate a sump full of oil, as with the proven Comstock solution which is the way I went on my Combat engine.

seattle##gs · Oct 22, 2016

I have a P11 motor...would the Comstock breather fit on this motor?

comnoz · Oct 22, 2016

seattle##gs said:
I have a P11 motor...would the Comstock breather fit on this motor?

Yes

Matchless · Oct 22, 2016

It would fit on the engine, but I would check that there is enough room. The gearbox on that model is very close to the back of the crankcase.

seattle##gs · Oct 22, 2016

I would install it where the sump plug is. Still enough room?

comnoz · Oct 22, 2016

seattle##gs said:
I would install it where the sump plug is. Still enough room?

Should be no problem with the sump plug style breather.

A rear case style breather will fit also but it would be tight. And of course it would require an engine teardown and machine work. Jim

case reed breather

comnoz

ewgoforth

comnoz

swooshdave

MFB

comnoz

xbacksideslider

jseng1

comnoz

madass140

jseng1

Dances with Shrapnel

guest76

Guest

seattle##gs

comnoz

Matchless

seattle##gs

comnoz

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