GY6 and the breather tube

[surfborg]

Hello Dawgs,

Some of you may recall that last year I (and others) had recurring problems with excessive oil blowing out the value cover breather tube. I've heard everything from: negative air pressure from the airbox forcing oil out the tube( I've disconnected the breather tube, no effect) , too much oil in the engine (also not true, it will blow out until most all oil is gone) and various other ideas.

Today I noticed an engine for sale on ebay (it was a Wildfire 150cc replacement engine) I noticed that in the photo of the engine it showed a tube going from the valve cover breather and routed across the top of the engine and then going down into the top of the CVT case. I wondered what would happen if I took the tube from valve cover and got myself a connector and mated it to the tube I have coming out of my CVT case. What do you guys think?

Surf

[sussexscooterhead]

I've seen those same pictures and think whoever set up that engine for it's photo session made a mistake.

I don't really understand why there is so much confusion surrounding the crank case breather tube. There is a ton of information online as to it's purpose and why it's necessary.

Without a breather tube (vent) of some description, an engine's crankcase would be a closed volume.

For more than one reason, the pressure inside the crankcase will rise during the operation of the engine.

Considering we're trying to seal oil within the engine, having the pressures inside the crankcase is a bad idea as it will encourage the seals to leak.

Furthermore, pressure inside the engine will rob it of power and cause it to run at higher temperatures.

Connecting the vent tubes of the engine and the rear transmission makes zero sense. Both parts of our scooters are intended to to run at something as close to atmospheric pressure as possible. Joining them together only ensures they both run at the same elevated pressure.

It would be likely, as well, that with the tubes joined, the transmission would eventually become contaminated with engine oil.

Did you have a problem with the set-up illustrated in the picture I sent you?

[surfborg]

I came to the same conclusion after more thought. I should of figured that out right away. I realized what that other tube was for. I just want to allow the crankcase to vent without spraying several ounces of oil all over the bottom of the scooter and my rear tire. The only service guys I have available to me have no idea what to do. I realize that some oil is going to make it out. I am also pretty darn sure that the amount I'm losing is not any where near normal. Let me explain. I fill the oil to the correct level and in the correct fashion. I have a 15 minute drive to work. 10 of those minutes are at 50 mph and the remainder is under 35 mph. I work a split shift so I make the round trip 2 times a day (in fair weather) That gives me 60 minutes of riding per day. The next morning when I check the oil I will have 1/3 less oil then the day before. If I were not to add oil, after 3 days it would no longer show on my dipstick. The oil coming out of the breather tube at that point will slow down considerably, but will not stop. I suppose I could run it down that low and then sell it to the first sucker that comes my way. Perhaps I could just ride it until the engine blows. I don't really like either of those options. Am I wrong for wanting to correct the situation? I suppose I was crasping at straws with that post. If I had discovered ScootDawg before I got the bike, I would have made different choices. Alas, that was not the case.

[Aaron]

I wonder if it would be possible to hook it up to the bottom of a top vented "bottle" type container and have it work like a radiator overflow vessel. It can breath under pressure but once it cools the oil could drain back into the motor.... any of you more able mechanics than I have thoughts on this?

[surfborg]

acd said:

I wonder if it would be possible to hook it up to the bottom of a top vented "bottle" type container and have it work like a radiator overflow vessel. It can breath under pressure but once it cools the oil could drain back into the motor.... any of you more able mechanics than I have thoughts on this?

That was one of the ideas I had considered. I even purchased a gerbil water bottle at walmart last night. I figured that perhaps I could grind down the metal straw and remove the ball inside (it's to keep the water from leaking out) and then drill a few holes up in the top to let the gasses escape and then let the oil drain back down the straw and back down to the engine. Might keep my privates warm in the cold mornings.

Surf

[Aaron]

Let us know how it works Surf.. I don't see the downside to it...but I am an idiot LOL

[natefromogden]

It concerns me that your engine is pushing so much oil out that breather tube. Mine blows just the littlest amount of oil, hardly any. I have a plastic, snap-topped box, (think band-aid box) that I installed a simple tube fitting into the side and drilled a few vent holes into the top. I built a little bracket to hold it, above the engine, in the area that the original airbox occupied.

After days of running my little box barely needs wiping out. I don't know why your motor blows so much oil, but you might just try raising the vent tube higher in relationship to the engine.

[earlwb]

On many engines, they put on a "oil catcher" of some sort. The oil catcher is intended to collect the excess oil mist that comes out from the engine when it is running. It allows the oil to condense inside and not to be spewed out all over outside the engine. From time to time you remove a drain plug and drain it out.
I have a oil catcher on my scooter and I also have one on my Harley too. I used a white gas fuel container like they use on the camping stoves. it is aluminum and has a cap on it. I simply inverted it, and drilled a couple of holes to fit a couple of brass tubing nipples from the hardware store. I made a bracket to bolt to the bike, and then a couple of long nylon cable ties, and I was in business.

[ryan_ott]

I am using a vacuum resivor from the cruise control of a car, drilled 2 holes for fittings. Have you ever took your valve cover off to see if the factory forgot any of the baffles?

[sussexscooterhead]

The valve cover on my engine has sort of a baffle system that (I think) is meant to allow the oil mist to drop out of the vapor exiting out the vent tube. I wonder if your valve cover is missing this baffle arrangement?

I also wonder if, for one reason or another, your engine suffers from more blowby than average and is expelling more vapor out the vent tube as a result.

I think the water bottle idea is going to work well for you, though, and would consider adding a bit of steel wool into the bottle to sort of capture the oil as well - a couple of those stainless steel or copper dish scouring pads might do the trick. Just a thought.

[sussexscooterhead]

LOL

Once again Ryan and I were posting at the same time.....and thinking alike!

[ryan_ott]

That happens often

[ryan_ott]

Here is the baffles of my RX200

Here is my catch can

[Dennis D]

I may be wrong, but I don't recall any baffle system like that inside of my valve cover, and I don't have a problem like surfborg does, with mine. My oil level drops a negligible amount the first couple times I ride after an oil change and then stays the same for quite awhile. When it begins to drop a little again, it's usually about the time I figure it needs to be changed anyway.

[surfborg]

I think I will check the inside of the valve cover. I wouldn't be suprised if a number of units came off the line with a problem like that. I'll just drain the oil and check that out. I'll do that before I continue. Be back in a few.

Surf

Okay.... that was a bust. The valve cover looks just like the photo above. Time for the gerbil bottle. Fred Flintstone would be proud.

Surf... again.

[jose]

I did the same as using a band-aid box with small holes along the sides, and one 1/4 inch for the breather tube. Along the inside of the band-aid box, I inserted a small wad of tissue paper to collect the oily blow-by. This takes my scoot about every oil change to change out the sightly wet napkin in the box. Simple and easy to get to. I did this because I had removed the original air box and installed an air filter along the back of the carb, no longer a front end air feed, which is then hose directed via the along one side and u-turn into the carb.

Jose'

[surfborg]

Okay Dawgs. I finally took a real close look at this and something natefromogden wrote popped into my increasingly fried brain "you might just try raising the vent tube higher in relationship to the engine" I thought about this. I decided to reinstall the vent tube back to its original position going up to the airbox. What'd I find? The tube didn't go very straight. Looking at it from the front I realized that it was a bit too long. It dipped down too far and any oil draining back down to the engine would get bottled up until it over filled the air box and spilled out the air intakes. I removed it again and installed a clear tube that was shorter and a more direct route. I drove for a few minutes to check for leaks. I can see the oil seeping back down towards the vent now. I'm going to keep checking it. Wish me luck guys. If this doesn't work, then I'll do the bottle thing.

Surf

[tieso]

I haven't paid much attention to the case breather tube on my Magster GY6 150. I know they come stock with a low grade rubber black tube that dry rots rapidly even when you keep the scooter stored and only ride it in dry weather. On a Magster case it's also placed on the very back of the CVT enclosure.

I've actually made a hit list of components that my bike actually needs as a result of low quality stock designs.

• The current stabilizer
  
• A "performance air filter and inlet tube to get rid of the bulky piece of garbage that blocks access to most of the engine space.
  
• A premium grade rubber case breather tube with a fitting tube filter.
  

Also every scooter I've dealt with over the past two years came off the lot with poorly tuned carbs that constantly over flowed the reservoir tubes; they aren't suppose to do that even with a throttle happy rider. Also the Throttle's are always poorly tuned which is why most scooters idle so low they stall out no cold starts. All GY6 engines I've worked on have liberal stock clutches that allow proper idle RPM's.

[natefromogden]

surfborg said:

Okay Dawgs. I finally took a real close look at this and something natefromogden wrote popped into my increasingly fried brain

Thanks for the kind words.Glad to help. I am pretty certain I have a picture of my installation but I can't find it. When I do, I'll put it up.

[surfborg]

I have good news and I have bad news. The good news is that I'm not loosing the oil out of the breather anymore. The bad news is that it seems to be coming from elsewhere now. Grrrrrrrr.

Surf

[tieso]

Sure it isn't dirty gas? My whole case was covered with black grudge before I tuned my carburetor and emptied the overflow tube.

[surfborg]

tieso said:

Sure it isn't dirty gas? My whole case was covered with black grudge before I tuned my carburetor and emptied the overflow tube.

The weather has went on a chilly streak out here. The scooter has been in the shed for a couple of days. I took a look out there today and my new clear shorter breather tube is doing the job. When I parked it in the shed tuesday morning (a storm was coming) I took a looked at the tube and I could see the coating of oil all over the inside today that coating was gone, it had all drained back to the engine. I cannot belive that after all this time I had not thought to examine the shape and path of the hose. Arrrggghhh!

Surf