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Found this today on the Rising Sun Cycles website:

NAG Crankcase Pressure Relief

In most internal combustion engines, it is best to maintain pressure within the engine crankcase below atmospheric pressure thereby reducing leaks through gaskets and seals from the crankcase to the atmosphere. And so as not to rob any horsepower driving the unnecessary air pump created by piston movement. You do not want the crankcase vacuum to be excessive, which would cause out side air and debris to be pulled through any worn crankcase seals or gaskets. The NAG Crankcase Pressure Relief Valves maintain a slight crankcase vacuum and maintain a negative vacuum at any engine speed or load.

NAG01-105VTR1000SP1/SP2 exclusive use


VTR1000SP1/SP2 exclusive use for 12φ street
(Blow off valve combined use is recommended)
Adaptation item turn NAG03-104
 

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Discussion Starter #2

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Might help if they had translation by another source than Babelfish.... were you actually able to understand their explanation? Jeezus H Krist!!!!
 

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I don't think it's very useful unless you have an engine in a very high state of tune where every single little thing helps.

PS: Nag is a pretty unhappy choice of name for a performance part... :rolleyes:
 

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I wouldn't mind finding something to help reduce the engine braking for my VTR, not sure if this would be of any use as the explanations are so unclear....
 

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I wouldn't mind finding something to help reduce the engine braking for my VTR, not sure if this would be of any use as the explanations are so unclear....

the engine braking is what makes the RC51 best for me. i hate the fact my R1 has no engine braking it is hard to get used to and my style like letting off the gas and slowing down more then having to grab brakes to slow down
 

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I wouldn't mind finding something to help reduce the engine braking for my VTR, not sure if this would be of any use as the explanations are so unclear....
Hey mikstr,

Not to be a smart ass... but, isn't that why so many have choosen "Slipper Clutchs"? So my guess is, you do Not have one, Do you ever think about one of these maybe?;)

Crank case pressure relief valves will help as the RPMs increase. "I Think" It will NOT do a thing for engine braking, as "Engine Braking" happens in the cylinders(s), off the gas, not in the engine's crank case...?;)

I don't have a slipper, norr do I want one, what I have done instead is, I've raise my idle alittle and best of all is> how friggin' easy it is to Feather my AWESOME Thorsten Clutch!:clapper
 

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I would love a slipper for my VTR, but to my knowledge no one builds one (talking Superhawk/Firestorm here, not RC51/SP). Of course, if you know someone who does offer one please share.....

As for the crankcase vs cylinder effect on engine braking, I agree 100% (hence the by-pass circuits used in the FI systems of various engines). Given the horrible translation, I was hoping perhaps it was a similar engine vacuum overrride system (similar to what Harris offered at one time).
 

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At the last Stage of Rebuild of my Engine I had drilled a 2nd huge hole (~ 1") into the crankcase, between the 2 Cylinders, and mounted another Breather there ( bit more difficult to realise, than it sounds ).

This Engine, of course accompanied with a few more other Mods, was incredible strong ( this Engine was the initial mental spark to realise TC finally )

Dunno why, there was no major Mod, I suppose it was the collaboration of all these Mods, and as far as it depends on the Feeling, this last Stage of my RC 51 was somehow stronger or more scary than my V3.

And BTW : I like this Forum, even I do not have much Time to stop by, but I love the Enthusiasm, RVT Maverick ( from the first Days ), RC51Stunna are still here, miss Michael Wheeler for his Posts, cannot remember his Forum Name, MRGN ist still here - "calm down" should be the Sentence you shoul include, whenever you reply to his Post.

Well, it is 4 O'Clock in the morning for me, I'm in Denmark at present, for some kinda research of my own Soul, Tendency of worlds Economy + more to think + Tons of Danish Beer which do not want to do their Job ( or does it appear they do ?).

However, Denmark Wintertime is nice, especially with the Dogs.

Like to Participate, you like Winter ?
Here's the Blog, it is build in German first, but the Pics have their own Expression: Thorsten Durbahn
 

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At the last Stage of Rebuild of my Engine I had drilled a 2nd huge hole (~ 1") into the crankcase, between the 2 Cylinders, and mounted another Breather there ( bit more difficult to realise, than it sounds ).

This Engine, of course accompanied with a few more other Mods, was incredible strong ( this Engine was the initial mental spark to realise TC finally )

Dunno why, there was no major Mod, I suppose it was the collaboration of all these Mods, and as far as it depends on the Feeling, this last Stage of my RC 51 was somehow stronger or more scary than my V3.

And BTW : I like this Forum, even I do not have much Time to stop by, but I love the Enthusiasm, RVT Maverick ( from the first Days ), RC51Stunna are still here, miss Michael Wheeler for his Posts, cannot remember his Forum Name, MRGN ist still here - "calm down" should be the Sentence you shoul include, whenever you reply to his Post.

Well, it is 4 O'Clock in the morning for me, I'm in Denmark at present, for some kinda research of my own Soul, Tendency of worlds Economy + more to think + Tons of Danish Beer which do not want to do their Job ( or does it appear they do ?).

However, Denmark Wintertime is nice, especially with the Dogs.

Like to Participate, you like Winter ?
Here's the Blog, it is build in German first, but the Pics have their own Expression: Thorsten Durbahn

Geez, nice to see you too Mr.T:D
 

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Discussion Starter #15
Good info and cool blog! This is a good site, it would be great if you would post here more often. Your expertise is missed!

I still need to get myself one of your monocoque SBK tail sections, Ill email you to discuss. :notworthy

Stunna

At the last Stage of Rebuild of my Engine I had drilled a 2nd huge hole (~ 1") into the crankcase, between the 2 Cylinders, and mounted another Breather there ( bit more difficult to realise, than it sounds ).

This Engine, of course accompanied with a few more other Mods, was incredible strong ( this Engine was the initial mental spark to realise TC finally )

Dunno why, there was no major Mod, I suppose it was the collaboration of all these Mods, and as far as it depends on the Feeling, this last Stage of my RC 51 was somehow stronger or more scary than my V3.

And BTW : I like this Forum, even I do not have much Time to stop by, but I love the Enthusiasm, RVT Maverick ( from the first Days ), RC51Stunna are still here, miss Michael Wheeler for his Posts, cannot remember his Forum Name, MRGN ist still here - "calm down" should be the Sentence you shoul include, whenever you reply to his Post.

Well, it is 4 O'Clock in the morning for me, I'm in Denmark at present, for some kinda research of my own Soul, Tendency of worlds Economy + more to think + Tons of Danish Beer which do not want to do their Job ( or does it appear they do ?).

However, Denmark Wintertime is nice, especially with the Dogs.

Like to Participate, you like Winter ?
Here's the Blog, it is build in German first, but the Pics have their own Expression: Thorsten Durbahn
 

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Well, my own Website is even confusing for me, it is very hard to find a special content, but I've had luck - found the Breather Mod Page.
Was hard to find, the Navigation is:
English Flag then
Click on "Recent" , then the very last Pic on this Page shows a small Thumnail , and from there you'll find the "Manual" how to do that.
I forgot that I pictured it and put it on my Weppage, but there it is !

I hope I can stop by more often here in the Future, it is still a funny and lively Place.
And regarding to get drunk with Danish Beeer: I decided to drink more in a shorter Period of Time...

 

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Thorsten, please correct me if I'm mistaken, but I thought the breather mod is really onlty beneficial on very high compression, high RPM motors. I've been led to believe that for lightly modded/stock motors it is worthless. Just curious, wondering what your thoughts are.

PS. THANK YOU for sharing your expertise and experience with the '51, it has personally saved my ass on a few occasions! :notworthy

Semper Fi! :rockon

-Rocky-
 

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Thorsten, please correct me if I'm mistaken, but I thought the breather mod is really onlty beneficial on very high compression, high RPM motors. I've been led to believe that for lightly modded/stock motors it is worthless. Just curious, wondering what your thoughts are.

PS. THANK YOU for sharing your expertise and experience with the '51, it has personally saved my ass on a few occasions! :notworthy

Semper Fi! :rockon

-Rocky-

Hey RockyMT,

No, IMHO this assumption is Incorrect, think about it Rocky....

Look at what the MC Companies have been doing for a few Years now, with 1st> Making windows in the Crank Case walls\webbing, in between the lower part of the Piston walls, into the Connecting Rods area, and then 2nd> They've gone to actually Openning Up those suckers "Windows" BIG afterwards!

They are always working to Reduce Crank case Pressure on their Stock street bikes = OEM Engines! ej;) So, it's not just for Built up, high Comp. Racing engines...:twocents
So by atleast adding Thorsten's "Big Breather Gasket" You are Definitely dropping Crank Case Pressure! (AS Long As You do it right!) I saw one for sale here not too long ago, I think Ben has it for sale, where the guy (NOT Ben) actually used a Rubber :wacky hose going off of Thorsten's BIG Breather gasket, Using this material IMO is CRAP! Wasted effort because whoever did this job actually might have made it Worse then OEM!..?


YES, I've done Thorsten's (what "I" call) Stage 1 "Big Breather Gasket" I know what I am talking about.;)
And here's the Reason it IS Crap to use a Rubber Hose on Thorsten's Big Breather Gasket: You've GOT to make a HARD 90deg. turn, running the hose IN Between the Valve cover-Head and Frame, heading the hose back to (where ever You plan to run it?)

Mine: I did My Thorsten Big Breather Gasket mod. approx. 5yrs. ago;
I ran mine back, then right up into the bottom of my Thorsten AIRBOX and Sealed the inlet = SWEET!
Using the "Rubber Hose" You could see in the picture, the rubber hose was being Pinched off, being Squished while making this Hard 90deg turn! So,..... Don't use a Rubber hose here and You'll be Golden!

Then there's (what "I" call) "Thorsten's Stage 2 BIG Breather Kit" which He has just pictured here yesterday (THANK You Very Much Thorsten and Thank You for the kind words Brother!) The Stage 2 Big Breather Kit is a major under taking BUT NO doubt a Great Pressure Reducer!....

However, I\We have seen quite a few Other ways to go about this, which are Much MUCH Easier to do, To reduce said Crank Case Pressure even further!


I Hope this Helps, What do You think?

Peace Jeff
 

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I don't believe a pressure differential with the outside part of the engine is good for seals or gaskets, but you can't assume that is 1atm.
At speed it varies. Then the pressure on the airbox is always less than 1atm but that is before the RamAir effect kicks in and raises it gradually!
So if at high speed you have +0.1atm in the airbox -0.1atm around the outside of the crankcase you have 0.2atm differnce through the seals and gaskets, that's about 2.8psi.

What hurts performance on singles and v2 engines is the slow breathing, air not moving fast enough in and out, not pressure. This translates into pressure stability which you don't have. This is also what happens when you raise the oil level, you decrease the air volume in there and the pressure variation becomes greater. Whether you can keep a higher or lower pressure in the crankcase if it is kept constant what ever it will rob off the bottom of the piston it will give back on the next stroke.

IL4 cylinders don't do this, as there is something coming down at the same rate something is going up, so the volume stays about the same, and they still need breathing as the air can't move fast enough from one side to the other to the other. I wonder what the Yamaha R1 Big Bang does?

There are some L4-L6 car engines, German ones come to mind first, that have a pressurized system, in other words when you open up the oil fill cap in the head there is pressure in there, in some there is in the head for flowing the oil back down the crankcase but not in the crankcase and use complex valving to do this.

If you were to fill up the crankcase of a single or v2 engine with fluid and seal it it wouldn't move, would it? Or not until something broke. An L4 would move but still very slow. That is how important quick breathing is. So, would this also mean the lower the pressure in there, the thinner the air, the faster it would move?
 
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