One way breather valve differences

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Good advice Peter, I am going to return it for a refund.
Right now I continue to have the XS650 installed, and it seems to be working fine.
I have it installed in the breather line at mid battery level, and then have another line exiting from
the valve and going out of the battery box and down to the chain area.
I have thus bypassed going back to the oil tank.
I guess it see no reason to return any contaminants to the oil.
What do you think of this?
 
I'm trying to keep an open mind about this - convince me of its real value compared to enlarged breather ports into the timing cover & exit etc


Hey Jim, To help convince you about the effects of a reed breather. Take your bike and put it in gear with the ignition off and roll it down a hill. See how many rpm you can get the engine to turn. Then take both plugs out and go down the same hill and you will find you cannot turn the engine nearly as fast. The reason is the power required to pump the air in and out through the spark plugs holes. Just the same as trying to pump the air in and out of a crankcsae breather hole but not as dramatic because of the low compression ratio in the cases. To eliminate all pumping losses in the crancase the open breather hole would have to be the same size as the combined area of the bores. So add a one way valve and eliminate 99% of the pumping losses and loose a little windage also because of reduced air pressure in the cases and it's a win-win situation without even thinking about oil leaks. Jim
 
In just the relatively short time this forum has been around the concept about crankcase breathing has been beaten to death.

If you want to really know more you should read some of the several threads that have been previously written.

Here's a couple key ones:
crank-case-breather-t3680.html?hilit=crankcase%20breather
how-can-you-have-some-extra-power-with-pcv-valve-t4814.html#p43408

comnoz said:
Several years ago when looking for some extra power on the racebike I thought a bigger breather would be the thing to do. The bike was on the dyno in my shop. I removed the fitting from the back of the mk3 engine case with the 3/8 inside diameter and drilled and tapped the the hole for a 1/4 inch pipe with a 1/2 inch inside diameter. And guess what- I lost about 1/2 horse. I went back to the original size to double check and got it back. Then I started going smaller on the fitting restriction and I gained power all the way up to the point of blowing oil out of the mainseal because of crankcase pressure. This proved to me that there is power lost due to pumping air through the restriction. The less air that was allowed to move the less power was lost. Installing a check valve got everything right . I kept the engine from leaking and got rid of the pumping losses and reduced the air drag in the cases. I saw about 2.5 horse gain over the open breather . The next season I installed a crank driven vacuum pump and got the power increase up to around 4.5 horse. Jim
Click to expand...

Once I read that I really understood what the goal was, eliminate the pressure from the crankcase. You don't do that by making bigger holes, you do that by pushing the air out and not letting it back in. A PCV valve might work for a little bit but it will most likely fail either at higher RPM or over time as it's not designed for that kind of abuse. A reed valve does exactly what you need.
 
So it has to run out of the crank cases - its worthless through the timing cover? Pressure would still pump in & out of timing side case through exitsing holes - dragging down the motor compression release style as described so eloquently above by Jim C .

Got in late on this one. Sorry for the bonehead newbie stuff.
 
Jim, Running the reed breather out of the timing case dampens the pulses from the pistons to the point where the reed doesn't work well as the RPM goes up. I block all holes into the timing chest and drill a new small oil return hole down low. This effectively makes the crankcase volume smaller and makes the reeds more work more efficiantly . Jim
 
Changing one every 5 thou or so should be considered a standard Maintanance practice.
Click to expand...

Not on my Norton. Changing crankshaft seals every 5000 miles has NO effect on crankcase pressure. You can change seals every time you start up. Makes no difference. It's the pressurized crankcase that passes oil through the seal into the primary. Eliminate the pressure and you eliminate the oil leak. Sounds simple enough to me.
 
I haven't put a crank seal in my bike since last time I freshened up the motor, about 35000 miles. I run a ventilated dry primary and it stays clean and dry. It's a metal cased seal put in with JB weld. Jim
 
Breathing out of the timing side may not be as good as the back of the case but I can say that it works well enough to stop those weeps and that's a fact. When I installed mine on my 850 MKIII I had a few weeps not really leaks. But now it is oil tight and I don't get the oily residue around the front of the fins or the rocker covers. Maybe it would be different if I rode it hard but I have other things to ride if that's what I'm after. Have a great weekend guys and ride safe, Chuck.
 
No question Chuck, any one way valve is better than an open breather as long as the opening pressure is light. Jim
 
comnoz said:
I'm trying to keep an open mind about this - convince me of its real value compared to enlarged breather ports into the timing cover & exit etc


Hey Jim, To help convince you about the effects of a reed breather. Take your bike and put it in gear with the ignition off and roll it down a hill. See how many rpm you can get the engine to turn. Then take both plugs out and go down the same hill and you will find you cannot turn the engine nearly as fast. The reason is the power required to pump the air in and out through the spark plugs holes. Just the same as trying to pump the air in and out of a crankcsae breather hole but not as dramatic because of the low compression ratio in the cases. To eliminate all pumping losses in the crancase the open breather hole would have to be the same size as the combined area of the bores. So add a one way valve and eliminate 99% of the pumping losses and loose a little windage also because of reduced air pressure in the cases and it's a win-win situation without even thinking about oil leaks. Jim
Click to expand...
hi comnoz,with all due respect i think your explanation to jseng is wrong ,you would,nt need a hill ,push a commando down your drive ,in gear with the plugs in and you would,nt get the motor to turn one rpm,take the plugs out and you could push it around all day,i think you got your 4 stroke mixed up with your two stroke ,back in the day,and maybe on modern 2 strokes i dont know we had compression release valves that effectively(took the plug out )and made a very effective brake when going downhill ,on 4 strokes there was compression release mechanisms that effectively(took the plug out)to ease starting on big singles
 
Sorry Chris, try it and see. I have. Of course I have a rolling road [chassis dyno] so my neighbors don't think I am delerious. Jim
 
Of course living in Colorado helps a lot going down mountains, in Florida, that would be pretty hard to do :mrgreen:

Jean
 
I think we have two types of results some are looking for here, Some that just want to stop the nagging weeps and some that are looking for a few more horses. No doubt the reed valve off the timing side will not do much for the latter, So maybe if you want total all out performance you will need to think of something as Mr. Comstock has developed, No doubt he has spent a lot of time and effort, Not to mention money on the parts he makes. For those of you that race I would think he is the guy you might want to talk to. Trial and error are the foundation of development. We need to appreciate there are some that spend the time and money to do so, I myself don't think I have the patience to do that or the money. But one thing I can say for sure is that we can all learn from each other no matter what we are looking for, That is why I check this forum daily. Thanks to all of you guys that share your thoughts, We may not agree on all these things but we have one thing in common and that is our Norton's. Lets keep them on the road. Ride safe, Chuck. :wink:
 
Comnoz - I have believed in the advantages of using a one way valve to create a vacuum in the crank case for a few years, since I started fooling with those "Krankvent" devices, however after reading some of the entries on the Bunnbreather blog recently, I wonder if he doesn't have a point about the advantage of having another one way valve to allow fresh air into the crankcase on the upstroke. Perhaps I'm wrong, but it seems that there would be some additional power loss from the suction on the pistons as they tried to move up the bore from a crankcase at vacuum and this could be eliminated by another one way valve letting air in. Have you ever done any experiments with such a system?
 
sidreilley said:
Comnoz - I have believed in the advantages of using a one way valve to create a vacuum in the crank case for a few years, since I started fooling with those "Krankvent" devices, however after reading some of the entries on the Bunnbreather blog recently, I wonder if he doesn't have a point about the advantage of having another one way valve to allow fresh air into the crankcase on the upstroke. Perhaps I'm wrong, but it seems that there would be some additional power loss from the suction on the pistons as they tried to move up the bore from a crankcase at vacuum and this could be eliminated by another one way valve letting air in. Have you ever done any experiments with such a system?
Click to expand...

Pulling fresh air into the crankcase effectively makes an air pump, which is totally counterintuitive to reducing pumping losses.

The reed valve doesn't actually create a vacuum, rather is makes the crankcase neutral, if I understand it correctly.

Bunn seems effective because they are comparing it to the stock setups which is woefully inadequate. Bunn vs. reed would be the real comparison.
 
comnoz said:
Jim, Running the reed breather out of the timing case dampens the pulses from the pistons to the point where the reed doesn't work well as the RPM goes up. I block all holes into the timing chest and drill a new small oil return hole down low. This effectively makes the crankcase volume smaller and makes the reeds more work more efficiantly . Jim
Click to expand...


If you drill at hole low in the timing side case, how does oil get the the cam chain etc if the oil is drained in the timing chest?
How big a hole & where?
Jim
 
sidreilley said:
Comnoz - I have believed in the advantages of using a one way valve to create a vacuum in the crank case for a few years, since I started fooling with those "Krankvent" devices, however after reading some of the entries on the Bunnbreather blog recently, I wonder if he doesn't have a point about the advantage of having another one way valve to allow fresh air into the crankcase on the upstroke. Perhaps I'm wrong, but it seems that there would be some additional power loss from the suction on the pistons as they tried to move up the bore from a crankcase at vacuum and this could be eliminated by another one way valve letting air in. Have you ever done any experiments with such a system?
Click to expand...


Allowing a small amout of fresh air into the valve cover would tend to scavenge the crankcase of blowby gases and may be of some value in keeping the crankcase clean and free of moisture from combustion byproducts. The reed valve on the case does create a pretty significant vacuum in the crankcase but any power lost pushing the piston up against this vacuum would be recovered on the downstroke. Compressing and releasing air uses very little power whether it is above the piston or below the piston. The only power loss is given up as heat. Moving air from one vessel to another through a restriction does take a lot more power but the small amout of air being moved through the engine through a small restriction in the valve cover [like 1/16 inch] would be insignificant. Jim
 
If you drill at hole low in the timing side case, how does oil get the the cam chain etc if the oil is drained in the timing chest?
How big a hole & where?
Jim

Jim, I modified a timing cover with a Lexan window to see what was happening in the timing chest when running the engine at speed on the dyno. [looking for power on the racebike] What I found was the timing chest was full of oil right up to almost camshaft level. Next I found that the oil in the timing chest got so hot being whipped by the gears that it exceeded the melting point of the Lexan window and made a mess. [ever wonder why the points cavity seal gets hard so quick] At that point I drilled a new hole down near the oil pump and plugged the last old hole. There is a picture in one of the ealier postings. With the new hole the oid level ran about crankshaft level. There was still a major amount of oil being thown off by the gears and lubing the cam is not an issue. And now with the lower oil level the oil temp would stay below the melting point of the Lexan. I have since been doing this on all my builds. Jim
 
I had wondered about the oil level being unnecesarily high in the timing chest. No way to drain until the oil gets all the way up to the breather holes. And the oil pressure release on most Norts (Atlas & Mk3s) dumps into the timing chest - thats a lot of oil dumping onto a spinning crank creating heat. Raises the question about the PRV dumping into the timing chest or re-routing back to the oil intake line.

Where is the photo you mention - or at least tell me how big a hole you drilled near the oil pump.

Jim
 
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