Which is the best "Comnoz" breather??

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I had seen that Jim comnoz had done two kind of breather , the one which fits 200.000 TO 230.000 as supplied by CNW which in place of the previous one , and the one which fits in place of the sump plug , is there any difference in performance and if the first one is better , is it possible to fit it on a 850 case ?
I imagine easily the second is a bolt on , but is it necessary to plug the timing side "holes" to benefit of the claimed performance ? Could we imagine the "Jim"'s sump plug breather plus an XS on the 850 timing case , or is it counter -productive ?
As you had noticed , I am lazy ,and don't want to dismantle my freshly installed enine , to plug the holes in my 850 timing case!
Thanx for your ideas.........
 
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I pestered Jim to get the real facts of the matter made plain as day, there is no real advantage to any of the PCV devices, as long as they draw down a bit below ambient. Next issue is what you want to pay and how hard to install. Third issue is how much bragging rights, after easy to obtain oil tightness, you can report by a meter how low it did go. If too effective they can suck oil out too or oil seals inside out.
 
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Pretty much if you have a 72 then go with the one at the back of the case. If you have anything else go with the sump plug. Simple, eh?
 
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I can chime in as I just installed the sump plug breather.

I am not going to offer any "professional" advice as to any breather or why or etc. I don't think I will have the ability to give professional opinion in my lifetime with these bikes. There's alot of stuff going on in there and I just don't feel confident in giving advice about everything. I can however share my experience.


I had an issue with crankcase breathing. I still *may have an issue. But I am working it out and dedicating TONS of time and energy into learning the bike and how the breathing system works from the top down.

I was having issues with the oil coming from the crank to the primary. I discovered the primary seal was blown out due to increased pressure in crank case.

Jim sent me a breather and I installed it. I noticed the oil still coming from the crank to the primary though.

I noticed a new leak though as well, this was coming from the oil lid in the oil tank.


Now I could have thought that the breather wasn't working or something like that but instead of jumping to conclusions I have been deducting conclusion from the symptoms.

I came to a realization the other day that the leak created from the oil cap must be increased pressure in the oil tank. This only happened AFTER I placed the breather in. The original timed breather did not create pressure in the tank sufficient to get by the oil lid seal. Now after this I ask myself why is there pressure i nthe oil tank? Well there was blockage in the tank breather.

So all said and done right now I only have one test ride but it was for 70 miles and things ran really well, I haven't checked yet but I suspect the primary did not get oil from the crank. I suspect this as my left leg is dry :)


Amount of pressure:
I dont know HOW much crank vacuum pressure the sump breather makes but it was alot more than the timed breather. I know it is a big difference as I noticed the oil coming from the cap when the oil tank breather was kinked.

Ease of installation:
You literally screw it on. It's got a fitting on the side for the breather tube that you tailor how it fits but that's it.

Quality of materials:
This thing is solid. It is machined beautifully and as well as solid it is discrete. It site where the sump plug goes so it is unnoticed. This also eliminates the tube going to the side of my timed breather.

175 bucks, now that's a healthy chunk more than the other breathers out there. But I think in my case going from the timed breather I did not have to do anything with the case so it was simple easy and I didn't have to rock the boat to install it. I can also take it off easy as well :)


IMG-20120809-00520.jpg

IMG-20120809-00519.jpg
 
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Kenny Dreer supplied inline $100 Krank brand that works for my Combats in barbed ends or threaded. Of course point awarded to support our vendors.

images

images


Then there's the cheap disposable Mini Might Motor Brake ventor with build in elbow and two size hose barbs that make the turn of vertical to horizontal into tank. Similar to this one but more compact subby
31HPZFC77EL._SL500_AA300_.jpg
 

batrider

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If you have a '72 then you have to go to the one in the back of the case. There is no giant sump plug!

Oops Swoosh already said that sort of. Yeah what he said!
 
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hobot said:
Then there's the cheap disposable Mini Might Motor Brake ventor with build in elbow and two size hose barbs that make the turn of vertical to horizontal into tank. Similar to this one but more compact subby

Motormite did not last 200 miles on my bike...

Cheers,

- HJ
 
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Same here. It's more of a placebo than a PCV valve when used on a Norton.
 

comnoz

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marinatlas said:
I had seen that Jim comnoz had done two kind of breather , the one which fits 200.000 TO 230.000 as supplied by CNW which in place of the previous one , and the one which fits in place of the sump plug , is there any difference in performance and if the first one is better , is it possible to fit it on a 850 case ?
I imagine easily the second is a bolt on , but is it necessary to plug the timing side "holes" to benefit of the claimed performance ? Could we imagine the "Jim"'s sump plug breather plus an XS on the 850 timing case , or is it counter -productive ?
As you had noticed , I am lazy ,and don't want to dismantle my freshly installed enine , to plug the holes in my 850 timing case!
Thanx for your ideas.........

Both units will create about the same vacuum in the crankcase. The unit that bolts to the rear of the case has larger ports so it draws down a little faster and gets rid of the extra oil in the cases at start-up quicker. It is nice because you can install it and forget it. It's pretty much out of sight. I would recommend it if the engine is coming apart for work or if you have the 72 case without a sump plug.

I built the sump plug breather for ease of installation. I just sent out the 100th unit. Thanks guys, Jim
 
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Hi Jim and others, many thanks for those answers, as said my engine is a 850, allready mounted , so the easiest way is the sum plug one, but good to know the difference in "performance", now how to order one ? i imagine send a PM to Jim....
But about the plugging of the timing side crankcase, I can take out the timing cover but if threading the holes that will make alloy entering inside.........so if letting like it , I know that it will reduce the performance of the system as the inside of the timing cover will create a supplementory volume , but if I let the breather tube at the upper rear of the case and plug in an XS, will that help , or will the two breather un necessary or as said previously "counter -productive" (mean working against each other, can't imagine as the pulse is in one way only , may be with a slight delay between inside of the case , and then the inside of the timing cover??) , would like to drill the small hole under the oil pump to help oil scavenging toward the case , but again some alloy getting inside.........I must have thought , before!!!
 

Holmeslice

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Both breathers are excellent, in my opinion.

Matt and Jim provided me with a CNW/Comstock breather bolted onto the back of the crankcase of my 750 race motor, and it doesn't leak a drop, living its life at sustained very high rpms.

I have installed probably 4 or 5 of the sump breathers on NYC Norton customers' bikes and they work fantastic as well. I installed one of the sump breathers on Jamie Waters' '73 Monocoque replica and we took it up to Canada and flogged the be-jeezus out of it, with not a drop of MLR40. (Doug MacRae took a wonderful photo of this bike, and perhaps he can post it. You can see the breather assy just protruding under the exhaust.)
 
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Not saying the breather is the only thing but I will give it credit for doing its job. My dad told me the only proof is if you can put your sandwich under the bike and take a picture. I didnt want to take the sandwich out so I placed a napkin under there....

IMG-20120828-00542.jpg


I can eat off my motor and I jsut rode in 40mi to work. If its like this when I get home today then I am definitely crediting the breather and of course a few other things...
using a catch can for oil tank overflow
rebuilding the oil pump lapping etc
replacing the crank oil seal with a stock one jbw in
flattening the valve covers
new oil lines

cant think of anything else....

Um yes I can think of something else, THE VALUABLE advise of the members of this site and JimC especially for stepping up and helping me out!!!
 

rvich

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I can't say this is a good idea...just an idea.

If you disassemble the timing side to give access to the holes. Get yourself some really sticky grease to put on your tap so that alloy shavings stick into it, you could thread those holes. Do the same with a bit for drilling and keep the speed very slow as not to heat the bit more than necessary. Breaking through to the inside is the critical moment. However, assuming you have the big sump plug, if you then flushed the case well before turning the crank, you would in theory get any bits washed out. If you have Combat cases, it would be a lot harder to flush. I have also necked down a shop vac to 1/2 tube so that it creates high velocity at the tip. You can get the tip in right next to the drill bit to suck up bits as they break loose. I have done this on things like transmission covers where a bolt has stripped and it needed tapped out. And while the results have been good, I would still be wary of doing it on my Commando cases. You decide.

Of course laying the bike down on the right side so that you worked from underneath it, would give you some help from gravity!

Russ
 
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The limiting factor in PCV is the mass of the valve to act fast enough and reed valve are about as good as it gets. Stronger pulses from less case volume and close mounted PCV would help the flappers move better, but my opinion is they still work ok if case volume opened wide to TS case or mounted near oil tank as should still relieve pressure below ambient before oil pushed out.

Crank case blow by shares pressure with head rocker boxes and TS case volume. In 750's [850??] there are two ~1/4" holes that connect to crank case, one up by the cam and another down below the pinon gear. Lower one sets the oil level for the cam and cogs to fling. PCV direct off crank case should not benefit by altering the TS case vents but by maybe sealing the top vent hole as sealing the bottom may not let new oil in and out. PCV off TS case would benefit with more or bigger vents for less pumping loss work through small hole. PCV below crank would help empty wet sump faster than the pump, as the Combat non-PCV breather design does. Make me wonder about the oil level and supply to the TS case if oil in crank case kept lower than the factory lower vent hole. Only significant oil that should get in then would be amount draining out of intake rocker box. Chain and cogs don't need but a misting to carry off grit though and less to dribble out cam seal into points cavity to outside.
 

rvich

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Sorry, sometimes once the brain gets going on something it is hard to shut if off. Obviously drilling the new drain hole is going to be harder to do without pushing some particles into the case. If before you plugged any other holes you drilled that one whilst using an air compressor to push air into the case it would be interesting to see if you could push the particles out whilst they broke free. Not plugging other holes first is of course to avoid blowing your seals out. It would be interesting to try this on something less critical to see how well it works. Got any old cases sitting around?

Russ
 

comnoz

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rvich said:
I can't say this is a good idea...just an idea.

If you disassemble the timing side to give access to the holes. Get yourself some really sticky grease to put on your tap so that alloy shavings stick into it, you could thread those holes. Do the same with a bit for drilling and keep the speed very slow as not to heat the bit more than necessary. Breaking through to the inside is the critical moment. However, assuming you have the big sump plug, if you then flushed the case well before turning the crank, you would in theory get any bits washed out. If you have Combat cases, it would be a lot harder to flush. I have also necked down a shop vac to 1/2 tube so that it creates high velocity at the tip. You can get the tip in right next to the drill bit to suck up bits as they break loose. I have done this on things like transmission covers where a bolt has stripped and it needed tapped out. And while the results have been good, I would still be wary of doing it on my Commando cases. You decide.

Of course laying the bike down on the right side so that you worked from underneath it, would give you some help from gravity!

Russ

I have drilled a few with the engine installed. I pressurized the cases with a blowgun and a ziptie loosely fit into the tach opening so the chips would blow out.
I have also plugged the large holes using tapered aluminum plugs driven into place with a hammer. I used some JB weld to make sure they stayed in place. Jim
 

Brooking 850

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Can anyone post a pic of the holes blocked and new one drilled please?
Jim, I have two of your breathers, first is on the Roadster daily ride and works a treat. Second will be on Bike #2 still being built
Regards Mike
 

rvich

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Hey Jim,
Isn't that top right hand hole in the photo for the wires going into the points cavity?

Russ
 
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