Reed Valve breather

I did the Old Britts conversion to the crank case on my 72 but I wasnt impressed by the little
plastic breather they suggested, so here is my version, its off a 600 Kawasaki mounted in my
adaptor plate.

Neat job, don't forget to drill a new drain oil lower so the timing chest is not filled with oil that may come out of your new breather. Check some of the posts on breathers, the info is there.

Jean (in HK between flights)

drain hole in what, I'm not sure what you mean.

ah ok, so maybe a small 2 or 3mm is called for in the lower part of the reed valve plate.

Hmm, I did the Old Britts thing, the only thing I am changing is a better breather.
I'm not dismantling my newly assembled engine to drill another hole.
I'll live with the consequences whatever they may be.

There's already a drain in lower TS case to set cam drive oil level and vents above that by cam as well as through the TS crank bearing 'restriction'. Don't understand the need of a reed drain hole if oil collects there at rest so what it should just pump it out with the blow by pressure as it does when running. Funny the metric cycle makers didn't think their valves needed it.

ludwig said:

I believe Jeandr is referring to this hole :

The 2mm hole I drilled is to prevent oil from pooling behind the reed valve , wich might hamper its operation .
May be of no concern in your setup ?

Do a search for Jim Comstock's ( comnoz) posts about the subject .

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I would not suggest doing the case mods for an engine with the reed connected to the timing chest. It will only work if the reed breathes directly from the crankcase. Jim

I would not suggest doing the case mods for an engine with the reed connected to the timing chest. It will only work if the reed breathes directly from the crankcase. Jim

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I may be a hillbilly now but once was educated in partial vapor ratios and gas pressure gradients on one way flapper valves, like circulatory systems and water pumps. I don't understand why it would matter where you put a one way valve in a Norton as long as its between the hi and low pressure gradients and above oil level. If the reeds need strong engine pulses to operate then how does it maintain well below ambient PSI and operate wit low density pulses at hi rpm?

My concept and way with Peel was increase the whole case volume by 3, 1/2" dia. vents to TS case, for increased volume diluting the pressure spikes, then PCV/Krank valve up near oil tank with its pick up mounted on ole magneto area. Total dry 5/8" breather hose w/o oil weeps spending 30-45 min in red zone upseting balloon tire hooligans and ugh THE Stuck Throttle Event that blew oil out all seams but nothing but dry vapors returned to tank.

Ideally one would want enough suction to both - keep cases below ambient and still pull some fresh air though head like next Peel will w/o a flapper valve. Likely a small 12 v air pump could do similar job and better than any check valve.

Hobot, what is the source energy to operate the reed valve? Would not locating the valve closer to the source be the more efficient? Not trained in partial vapor ratios, nor am I a hillbilly.

The idea behind plugging the holes between the timing chest and the crankcase is to reduce the volume of the crankcase. That makes for a larger spike in crankcase pressure every time the pistons are at BDC so the reed valve is more able to respond to the pressure pulses at cruising RPM and maintain a vacuum.

It is easy to create a vacuum in the crankcase at idle and low rpm by attaching a reed valve to the timing chest. And it is better than no reed valve at all. Unfortunately at higher rpm when the engine is loaded the pulses that make their way through the holes between the timing chest and crankcase are no longer strong enough to open the reed until the average pressure in the cases rises to a few inches.

Power is not the idea or concern. Oil leakage is. Particularly the main crank seal. Jim

Deja Vu all over again!

Duh, Dudes, don't confuse efficiency with effectiveness. I can kill a deer with an efficient .22 cal, just not as fast as with excessive wasteful big 30.06, both get the bleed to death job done in reasonable time. Point being yes a reed will work more efficient the closer ie: harder the pressure pulses, but so what, these strong pressure pulses tapper down to about nothing once the case pressure is pumped down well below ambient within seconds of running rpm. So yes indeed reed better close up - until you've blipped engine once on start up, then shouldn't matter a whit worth where its placed, other than interfering with oil drain or collecting condensation for oil mayonnaise. Personally my logic says to make the volume behind the check valve as big as can be to dilute the pressure spikes. If not enough pressure spikes to operate the reed or PCV - then so what - that just means there's also not enough pressure spikes and windage then to blow oil out or interfere with ring sealing help. Win Win.
So only thing I can see with reed placement is how fast it pumps down crankcase, on 1st warm up blip or on 3rd. More case volume means less chance or intensity of pressure spikes with reed skipping a beat with oil drop fouling at hi rpm. While yoose guys seem to want more pressure spikes in a smaller volume I think oppositely as usual.

Power is not the idea or concern. Oil leakage is. Particularly the main crank seal.

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Wish I'd had that little nugget of wisdom before I went on a crankshaft seal changing spree. Even to the point of finding a seal made of unobtainium, for which I paid dearly, only to have it leak.

JimC said:

Power is not the idea or concern. Oil leakage is. Particularly the main crank seal.

Click to expand...

Wish I'd had that little nugget of wisdom before I went on a crankshaft seal changing spree. Even to the point of finding a seal made of unobtainium, for which I paid dearly, only to have it leak.

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Jim,
I will be glad to send you a sump plug valve. You can try it and see if it cures your main seal leak and then pay me if it does or send it back if it doesn't. Jim

"I would not suggest doing the case mods for an engine with the reed connected to the timing chest. It will only work if the reed breathes directly from the crankcase. Jim"

I assume you mean blocking off the holes mod,
the Old Britts mod has 2 extra 3/8 holes , you think that is not enough "connection" between crankcase and timing chest
when using the reed valve?

madass140 said:

"I would not suggest doing the case mods for an engine with the reed connected to the timing chest. It will only work if the reed breathes directly from the crankcase. Jim"

I assume you mean blocking off the holes mod,
the Old Britts mod has 2 extra 3/8 holes , you think that is not enough "connection" between crankcase and timing chest
when using the reed valve?

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Yes, I was referring to plugging the holes and/or drilling a new return hole. I would not do that unless I had a reed directly on the crankcase.

Years ago I tried adding extra holes between the crankcase and timing chest to make the reed on the timing chest work better but I didn't get much improvement. That was on a later model engine.
If you have an early model engine with only one tiny hole into the timing chest then I would suspect extra holes would be needed to make a timing chest breather work at all. Jim

comnoz said:

JimC said:

Power is not the idea or concern. Oil leakage is. Particularly the main crank seal.

Click to expand...

Wish I'd had that little nugget of wisdom before I went on a crankshaft seal changing spree. Even to the point of finding a seal made of unobtainium, for which I paid dearly, only to have it leak.

Click to expand...

Jim,
I will be glad to send you a sump plug valve. You can try it and see if it cures your main seal leak and then pay me if it does or send it back if it doesn't. Jim

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Thanks much, Jim. It was some 8 or 10 years ago I was struggling with the crankshaft seal. I then discovered the reed type PCV valve. Needless to say, no more oil leaks. I very much appreciate your offer and if I didn't already have one I'd take you up on your offer.

JimC (not comnoz)

I am trying to figure out if your deer is spinning near red line will a .22 kill it at all?

rvich said:

I am trying to figure out if your deer is spinning near red line will a .22 kill it at all?

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If it has a reed breather it will. :?

comnoz said:

rvich said:

I am trying to figure out if your deer is spinning near red line will a .22 kill it at all?

Click to expand...

If it has a reed breather it will. :?

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That's funny!