05 450R head/crank breather hose/vent questions?
  • rodH
    Posts:38
    Joined:Thu Jan 26, 2006 10:42 pm
    05 450R head/crank breather hose/vent questions?

    by rodH » Fri Jan 29, 2021 5:27 pm

    I was working on my 2005 CRF450R last night (installing larger tank and radiators, more on this in another thread) and I remember that the last time I rode, it was pretty hard to start cold (after it was warmed up, one kick every time). So I wanted to see if that was a fluke, so before working on it, I tried to start it again. Turn on gas and choke, 3-4 throttle blips and tried to kick. No go. Finally took me probably 15 kicks to start it. Something isn't right, because when I got it out of storage 5 months ago, after it sat for a couple years, It started on the 4th kick, no problem. Same with the next few rides.

    As I was working on the bike, I noticed that the breather hose was completely black (full of oil). I remember reading something a while ago about how they can fill up with oil and if this happens, it can make it extremely difficult or impossible to cold start (I can't find the thread now). I unplugged it and quit a bit of oil came out. I tried to do an extensive search last night, but it is really hard to find much info on this. I have read that the hose can fill up if you over fill the engine oil (sure enough, my window was full of oil, so I must have over filled it, I guess. I also read that if you lay the bike down while it is running, it can cause the oil to overfill into the hose. I did have a crash where I laid it down and it ran for a bit (rekluse let it keep running). This ride, the bike was easy to start, since this ride, it has been difficult to start. So it may have filled up from overfilling the engine oil and/or laying the bike down.

    Sounds like many people are just leaving this valve open or putting some foam at the tip or buying the tokyo mods or applied kits, or even doing DIY solutions with a small filter at the end (allowing oil to seep out but not letting junk in).

    I am still not done with working on the bike, so I haven't been able to just drain the oil out of the tube and let it cool and then attempt to cold start again. I guess my question is, what is this hose for and is this really a common issue that makes it hard to start the bike when it is cold?

    TIA
  • Aussiecrf230
    Posts:1964
    Joined:Fri Jan 06, 2006 11:11 pm

    Re: 05 450R head/crank breather hose/vent questions?

    by Aussiecrf230 » Sat Jan 30, 2021 3:45 am

    Have always split the pipe in half for about and inch and a half so less chance of getting clogged.

    One of those items along with carb breathers that needs to be checked when cleaning or after storing for a while.
    Ray
    Australia

    CRF230F 2004
    C30F Power Up needle
    Mains 132
    Idle 45
    2 turns out
    Baffle out, Screens In

    It starts,it runs,it gets to where all CRFs can get to without the valve or valve plate dramas
  • rodH
    Posts:38
    Joined:Thu Jan 26, 2006 10:42 pm

    Re: 05 450R head/crank breather hose/vent questions?

    by rodH » Wed Feb 03, 2021 12:23 pm

    Have always split the pipe in half for about and inch and a half so less chance of getting clogged.

    One of those items along with carb breathers that needs to be checked when cleaning or after storing for a while.
    Great. Thx
    05 CRF450R
    TLD Graphics
    Pro-Wheels-Black/Red hubs
    Scotts Stabilizer
    Applied Triple Clamp
    Suspension by Jake
    Gold Pro-Tapers
    LightSpeed carbon disc covers
    PMB end cap/spark arrest
    Works Connection frame and Radiator protection
    Twin Air Power Kit

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