Xs650 oil breather

I have a '75 XS650. I have been having trouble with a decent amount of oil coming out of the breathers on the head and making a mess. The air box has been eliminated as i have a K&N big air kit on it. This is my first XS so i'm learning/figuring things out as i go. I assume Yamaha had some sort of built in system that will allow the crank to breathe but keep motor oil inside? My original thought was to plumb an automotive PCV valve and run a line down to the road in case any oil did make it past. Does anyone else have this problem? and what are some ways to fix it? Thanks in advance.

my shit breathes out a bunch. i forgot to put that oil breather baffle thing back in the head during my rebuild LAST time. i was told that that might help. also if you have too much oil it can pump out the top pretty good. i dont think it was a problem, but the "hey your leaking oil" shit got annoying, because it was coming out the breather tubes and not the engine which besides forgetting that piece i put that engine together with care and didnt leak a drop. when i put it back together this time there is no way that ill forget that again.

this dude

thanks, i guess i'll start by taking off the cover. i have all the parts to set up the PCV system, but my concern is knowing whether or not its working properly/allowing enough pressure equalization. I do NOT want o blow any gaskets or seals.

At first i didnt mind the oil, but it seemed like it was a lot more that "normal." but as far as leaking oil... its just leaving its mark. haha. my jacket is covered in little oil spots from the oil getting on the chain/tire.

Use a power brake check valve; it's been reported that it helps keep oil from pushing past seals etc.

I personally use the check valve, and since it's a 90* angle, I added an extra length of hose and routed it directly into the factory chain oiling hole on the left cover. Stock from the factory, the breather hoses were routed into this hole to put that burped up oil on the drive chain.

Do you have any idea what the difference between the Check valve and the PCV valve as far as how they operate? the PCV valve probably needs intake vacuum to work the valve properlyl; as they are typically routed back to the air box? I guess I will just have to continue to trouble shoot / try different options.

Originally Posted by jmcninch

Do you have any idea what the difference between the Check valve and the PCV valve as far as how they operate? the PCV valve probably needs intake vacuum to work the valve properlyl; as they are typically routed back to the air box? I guess I will just have to continue to trouble shoot / try different options.

My understanding is that the power brake check valve is a one way valve that maintains positive crankcase ventilation. I believe the automotive PCV doesn't offer this advantage, it flows both ways.

I've been meaning to try the power brake valve. From what I hear it works pretty well. Available in the Help! isle in most any auto parts store. One thing I found helps is keep the oil just a little above the lower mark on the dipstick. When I fill it to capacity it just blows off the excess oil down to there anyways.

I use this on found at MikesXS:



I pulled the inlet tube out and cut down the tube on the bike. Then pressed it on (real tight fit). So far so good. (Have to clearance the botton of the top tube so it doesn't hit the frame. Like a 1/4".

mine spits quite a bit of oil out the breather also no matter how much oil is in the motor. I have tried using less, etc. I just put a long hose on there that routes it down the backbone to the bottom rails of the frame and it spits it out there all over my battery box. Annoying as hell but I dont really care too much!

Seems like a common problem for some XS650s, and no one knows why. A '73 I used to have blew tons out. The '81 I have now is like bone dry. Just route the hose down to the ground or above the chain and you'll forget about it (until you see the sports on the garage floor).