FAO Grayracer - Oil breather mod


103 replies to this topic
  • grayracer513

Posted March 04, 2009 - 09:32 PM

#61

The vacuum formed due to a check valve is transient, and can't really rise beyond the level created in a single piston upstroke.

PCV valves are check valves, but they are closed in one direction and metered in the other, which they won't flow an adequate volume of air to be used for the crankcase breather on a thumper.

  • mike_dean

Posted March 08, 2009 - 01:56 PM

#62

Check out Gravesport.com and look at the oil separtor for the YZ450, made for high rpm supermoto but you will get the idea. part # aby-07y24-oask

  • husqy360

Posted April 23, 2009 - 07:47 PM

#63

so i did this mod last year and never seen any oil coming out from the filter, i do check it every few rides.

my question is, how can the oil go up the hose to the air box? wont it just go back or stay at the lowest place possible?

should i do the t mod to the mod i already did?

  • Goosedog

Posted April 27, 2009 - 06:58 PM

#64

my question is, how can the oil go up the hose to the air box?



When you crash and the bike's inverted.

  • husqy360

Posted April 28, 2009 - 09:59 AM

#65

When you crash and the bike's inverted.


what if i dont?

  • grayracer513

Posted April 28, 2009 - 10:02 AM

#66

Oil would eventually be blown out of the breather even if it ran perfectly vertical for 3 feet.

  • Aka.Goose

Posted May 13, 2009 - 12:18 PM

#67

Couldn't you use some kind of tapered/hose diameter reduction fitting right after the Y fitting for the oil draining/down line, so that it's thin enough to route with the carb overflows??? The smaller diameter down line would still help offset the very slight resistance of air flow from the filtered end in the air box under normal conditions, yet still drain, and go virtually unnoticed visually...

  • Aka.Goose

Posted May 13, 2009 - 05:31 PM

#68

Something like this:
Posted Image

  • TheHarp

Posted May 13, 2009 - 09:40 PM

#69

Check out Gravesport.com and look at the oil separtor for the YZ450, made for high rpm supermoto but you will get the idea. part # aby-07y24-oask


I have this on my 08 450 motard -- still blows oil...not a lot, but enough to notice.

  • Aka.Goose

Posted May 13, 2009 - 09:57 PM

#70

Yeah, like that, hahaha...
Posted Image
Come on now, can't somebody machine me something like this for WAAAY LESS than $90!!!
Jeeze...

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  • grayracer513

Posted May 14, 2009 - 06:32 AM

#71

Yeah, like that, hahaha...
Posted Image
Come on now, can't somebody machine me something like this for WAAAY LESS than $90!!!
Jeeze...

They can. There's one in the first post in this thread. A simple T is all that is needed, routed exactly as the OP has done, with the "straight-through" path running from the cam box to the downward tube. It simply doesn't need to be any more exotic than that.

If you insist that you want the down-routed leg a smaller diameter, there are plastic T's available in auto parts houses that are "stepped", so that they can be cut off at different points, resulting in a T with as many as 3 different size outlets.

  • Aka.Goose

Posted June 10, 2009 - 06:22 PM

#72

OK...Here's the parts I'm going to go with...a total of about $10...
The silver fitting over the breather tube is going to be the opening in the airbox to feed the tube through...It's a sink fitting adapter that just so happens to fit the breather hose perfectly tight and has a rubber seal to make it air tight...The T fitting is a little too big on purpose (pita to get the hose on) so that there is no inner diameter reduction at all...The other brass fitting is so the drain hose can be a smaller diameter and hopefully be routed with the fuel overflow lines...
Posted Image
Posted Image

  • 350warrior

Posted June 11, 2009 - 08:41 AM

#73

I think I will do this! Scary thing is, ive started my bike in water, but not deep. :|

  • Aka.Goose

Posted June 11, 2009 - 09:47 AM

#74

Ya, I don't think this mod would help in this situation, hahaha:
Posted Image

  • 350warrior

Posted June 11, 2009 - 09:50 AM

#75

LOL. Its a 2 stroke, oh well! :thumbsup:

  • Goosedog

Posted June 11, 2009 - 02:50 PM

#76

I think I will do this! Scary thing is, ive started my bike in water, but not deep. :|


I've done the same and it was deep (and muddy too). I was all freaked out until I did a total rebuild (for other reasons) and found the engines interior to be spotless, top-end and bottom.

Posted Image

  • Aka.Goose

Posted June 15, 2009 - 08:49 PM

#77

Did my mod today...
The breather comes over the spark plug cap and is zipped loosely to the throttle cables right where they cross over...
Posted Image
It comes back near the carb and T's...the down line gets reduced and exits with the fuel lines...the upper line gets routed through the gap in the top of the shock, and into the airbox passing through a rubber grommet...which is then capped with a $3 breather filter from AutoZone...
Posted Image
Posted Image
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  • spc mike

Posted June 15, 2009 - 09:02 PM

#78

Oil WILL make its way to that filter and get very messy, in and around it. just an FYI.:thumbsup:

  • Aka.Goose

Posted June 16, 2009 - 01:06 AM

#79

Yeah, that white filter crap isn't good, it's just falls apart in your hand easy...I don't want that to get sucked in...I'm going to get a little stainless filter to put on there...
I really don't think much oil at all will pass to the filter...will post results after some rides...

  • Chop Shop

Posted June 16, 2009 - 08:08 AM

#80

It seems to me that everyone is doing what the CRF450 comes stock with... except on the Honda the vent comes off the cam cover and tee's, venting open to a grommet in the airbox (no filter) and the catch line runs down beside carb and is capped off with a removable plastic plug.

The down tube is clear so you can see what weeps out. In my experience (4 CRF 450's) there is never more than 10mm of oil at the end of the line. I pull the plug and drain whenever I wash my filter.

Has anyone run a set up like that on the YZ450?





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