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JS Motorsport breather

Discussion in 'Norton Motorcycles (Modern)' started by ntst8, Apr 28, 2019.

  1. ntst8

    ntst8 VIP MEMBER

    Joined:
    Feb 14, 2004
    Have been away for a couple of days and Jims breather had arrived in the post while we were gone.
    I have a bit of a to do list but couldn't resist bumping this up the queue and fitting the shiny new toy this afternoon.
    JS Breather 1.JPG JS Breather 2.JPG
    Removed the dipstick and not surprisingly no chuffing with the engine running.
    Probably won't have a chance for a decent ride until the weekend, will update after that.
     
  2. BritTwit

    BritTwit VIP MEMBER

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    Aug 25, 2009
    Nice.
    Definitely prettier than the plastic separator.
    Can't wait for your report on it's effectiveness.
     
  3. TonyA

    TonyA VIP MEMBER

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    Jan 16, 2015
    I am considering its use on the new breather system that is on newer bikes - (No banjos on rocker cover) . My concern is its side effect on oil tank venting. My fears may be unfounded , but I would like to test this somehow . Will there be enough air for oil to flow out of and in to the oil tank , under all conditions and speeds ? Will another vent be necessary in the fill cap say ? Or route the existing oil tank breather to a catch bottle with a air vent ?
     
  4. Fast Eddie

    Fast Eddie VIP MEMBER

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    Oct 4, 2013
    Tony, am I correct in thinking that as standard the oil tank breaths via the engine?

    If so, then I’d say there’s nothing to worry about, if the oil tank and engine are at the same pressure, all should be perfect.

    Think about life with old Brit bikes before reed valve breathers, the engine was under a positive pressure and the oil tank was at atmospheric pressure, but oil still got pulled out of the tank by the pump OK.

    A bigger question for me is should the reed valve replace the oil separator or be used in conjunction with it? Given the one way nature of the reed valve, I suggest it should be fitted after the oil separator if used in conjunction.
     
  5. TonyA

    TonyA VIP MEMBER

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    Jan 16, 2015
    Yes , Oil tank vents through pipe back of head through push rod tunnels , through timing side and finally out the crankcase vent through air oil separator to air box. Air must enter the oil tank for oil to leave it . Not quite the same as Old Norton . Old Nortons had a tank vent to allow this. 961 Oil system will be sealed tight so to speak. Maybe unfounded , but I am not sure what may happen. And YES , air/oil separate first then check valve out to air box if possible. And then I wonder how much will drain back if that check valve seals tight oil will come out very slowly.
     
    Last edited: Apr 28, 2019
  6. BritTwit

    BritTwit VIP MEMBER

    Joined:
    Aug 25, 2009
    Well, I don't see how any oil can flow back past reed valve back into the breather.
    Valve only opens when venting crankcase pressure out to air box.
    This can only blow any trapped oil outside the reed toward the airbox.

    Someone on the classic forum with a 750/850 reed valve suggested drilling a tiny hole in the reed to allow a small drain back into the crankcase, but not big enough to allow a great deal of air to invade.
    Dunno if this would do more harm than good.
     
  7. TonyA

    TonyA VIP MEMBER

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    Jan 16, 2015
    I think that would ruin a great JS Motorsport check valve I'm afraid. Not a solution in my view. With the check valve just before air box , you just let the air box catch bottle pick up any discharge . Those are secondary concerns , Primary in my mind is will enough oil flow in and out of the oil tank with out a clear path to the air box.
     
  8. TonyA

    TonyA VIP MEMBER

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    Jan 16, 2015
    That's not what we're talking about. Its the oil in the separator allowed to drain out back to crankcase . Thats why FE asked should it be crankcase to separator , then to check valve then , out to air box.
     
    Last edited: Apr 28, 2019
  9. jseng1

    jseng1

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    Nov 26, 2009
  10. ntst8

    ntst8 VIP MEMBER

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    Feb 14, 2004
    Britwit - Ducati crankcase breathers have a small hole drilled in the breather body between the two reed valves, or at least the 10 year old one i have on the shelf does. It wasn't going to be an easy fit like Jims.
    I tried the motomite valve on my 850, before the two Jim's started offering theirs, and felt that it only worked very briefly so haven't gone there again.
    My hopes are that this will reduce the oil in airbox issue and perhaps the lack of pressure pulses in the airbox may also help the wandering idle issue, time will tell.
    My idle had settled down quite bit since the dealer had a play back in Feb, but was sitting around 1600 rpm typically. Yesterday on the minute or two in the shed and the 1/2 mile run down the road and back it sat at 1400rpm rock steady. Not yet sure i can put that down to the breather though. Will also talk with the dealer to make sure nothing they did in Feb will be upset by this.
     
  11. Fast Eddie

    Fast Eddie VIP MEMBER

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    Oct 4, 2013
    Iain, I’m pretty sure there’s no impact from breather pulses effecting the intake. Lots of bikes breath into the airbox this way. And the pulses are minor compared to those from the air entering the airbox and being sucked into the engine.

    As Tony has mentioned, it’s the possibility of any issues with oil tank pressure / feed that I’d be keeping an eye on I’m your shoes.
     
  12. ntst8

    ntst8 VIP MEMBER

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    Feb 14, 2004
    I agree air intake effects are likely wishful thinking.
    Mine has the original style breathers via the rocker cover. I can’t think of any way the reed valve would be bad for the oil tank or pressure feed side of things. On old bikes some claim the gravity draining of rocker area is improved with a good breather so hopefully not a step backwards here.
     
  13. TonyA

    TonyA VIP MEMBER

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    Jan 16, 2015
    Hello ntst8 , You should be fine as you say . The oil tank on yours will vent good through the l/h banjo to the air box. Its clear sailing for you . Its the new system I am worried about . Let us know if it helps the OIAB problem .
     
  14. jseng1

    jseng1

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    Nov 26, 2009
    Yes it should work well on the early models with the vent from the oil tank through the L/H banjo to the air box. Positive pressure is released and prevented from re-entering (thus reducing overall positive pressure). That means less pumping and less oil loss to the air box. What about the later models? Is it easy enough to retrofit them to the earlier version?
     
  15. Fast Eddie

    Fast Eddie VIP MEMBER

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    Oct 4, 2013
    If the oil tank connects to the rocker box and then to the airbox, then the engine gases can bypass the reed valve, both ways.

    Or am I reading something wrongly here...?
     
  16. TonyA

    TonyA VIP MEMBER

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    Jan 16, 2015
    No you're not wrong. The old system is not ideal either . In fact with tweaks , the new system would be better . As iwilson's test showed , when he releases the oil tank cap the crankcase pressure gladly vents that way with the old system. As he said least resistance path. If you looked at the old rocker cover baffle plate behind the L/H banjo you would see a tiny slot for the crankcase gases to go. By comparison the oil dipstick cap looks like a wide open barn door. In fact , when I think more about the new breather system has minimal gases going to the oil tank so most must be going in and out the air box so that part works. An experimenter should cap off the rear fitting on the rear of head and take that oil vent hose from oil tank to air (catch bottle) . Now you can run the JS check valve on the crankcase to air box line. This way you will separate oil from the oil tank and oil from the crankcase air box for your test.
     
    Last edited: Apr 29, 2019
  17. richard-7

    richard-7

    Joined:
    Feb 24, 2014
    See my manual OIL ROUTE
    https://coloradonortonworks.net/part-categories/961-norton-workshop-manuals.html
     
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  18. TonyA

    TonyA VIP MEMBER

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    Jan 16, 2015
    Hello Richard , Yes Oil Route is great manual and the only one of its kind . Very glad you made it !
     
  19. richard-7

    richard-7

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    Feb 24, 2014
    I made it for you. Remember?
     
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  20. TonyA

    TonyA VIP MEMBER

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    Jan 16, 2015
    I was looking at it again Just the other night ! I hope to see you later this summer too.
     
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