1982 GS450L -- Gas coming out of breather tube

[hiroyakamotosan]

Alright, I'm stumped. I searched all over the forums for answers to this problem and found a similar problem but no answers to my dilemma. I recently acquired this bike from my uncle. It has about 22k miles and hadn't run in about 2 years. I had to do a lot of minor work to it but I've go it running nicely and can ride it around.

My main problem is that gasoline vapors are coming out of the crankcase breather hose on top of the motor. I've already replaced the petcock and rebuilt the carbs after they fed a full tank of gas into my crankcase. My Haynes manual doesn't show much up for the breather tube area of the motor and I'm running out of ideas on why my bike is doing this. I read a similar post on oil and gas coming out of the breather tube and I think my problem is related if not the same. The only thing I can think of after doing all that is that a lot of gasoline is getting into the base from blowby. You would think that with nice compression on both sides that the rings are not the problem.

I just would like to bounce some ideas around before I finally go and rip the top half of the motor off. I'm a car mechanic so I have the tools and knowledge to do this comfortably, but I also don't want to go chasing false leads. Any thoughts, tips, or solutions would be great. Thanks.

Hiro

[Redman]

Welcome to GSR.

Not understanding how you notice gasoiline vapors comiing out of breather hose on top of engine. You take it off and smell it?

Tell us more.

In addition to replacing petcock, hopefully you also came to the understanding to not leave it in the PRIme position.

.

[tkent02]

Check your oil in the crankcase, does it smell like gasoline? Is there too much oil in there?
If it does you have gas going into the engine through the carburetors, usually caused by a faulty petcock. Either the petcock is not shutting fuel off when the bike is parked, or the diaphragm itself is leaking fuel down the vacuum line. Could also be you leaving the petcock on prime. When the oil gets thinned out by enough gasoline, it blows by the rings, into the head, and out the breather.
Change the oil, fix or replace the petcock, you should be good.

[hiroyakamotosan]

The way I noticed the gas was little wisps of what looked like smoke near the carbs. The "smoke" would disappear when I shut the motor off. So I pulled the breather tube out to where I could see it and there was what smelled like gas coming out of it.

I've already replaced and triple checked the petcock and carbs. The oil was changed just a week ago after the original petcock failed on me. Could running too rich or using a thinner oil possibly cause this? I'm using 10W-40 according to my manual.

Hiro

edit: Forgot to mention that while the oil has a hint of gas it is on the money level wise. My petcock isn't in the prime position.

[Postman_Pat]

The "smoke" you're seeing is almost certainly the crankcase vapours, which are generated when the engine is running.

The breather tube on the top of GS motors is a method by which these vapours are recirculated into the airbox. These crankcase gases often contain significant amounts of unburned fuel and water vapour. This explains why the "smoke" has a smell of gasoline.

Suzuki designed it this way mainly as an anti-pollution device.

It seems likely that your breather tube is not sealing properly, which is why you're seeing this gasoline-smelling "smoke".

Maybe you could replace that as a first step and see whether there is any improvement.

[BassCliff]

Greetings and Salutations!!

Hi Mr. hiroyakamotosan,

I'll offer a couple of suggestions. Is your breather hose cracked or loose? It should connect the top of the engine to the airbox. Is that airbox inlet clean and unclogged? Have you checked the float height on your carbs? Could it be that one of your floats no longer is floating? When you rebuilt your carbs, did you use any of those store-bought kits? Did you punch out the proper holes in the float bowl gaskets? Did you follow the GSR-recommended carb rebuild series listed below? OK, that's enough questions. I'll just shut up and say "HOoooowwDY!"

Here is your very own magical, mystical, mythical, mind-expanding "mega-welcome". Please take notice of the "Top 10 Common Issues", the Carb Rebuild Series, and the Stator Papers. Now let me roll out the welcome mat for you...

Please click here for your mega-welcome, chock full of tips, suggestions, links to vendors, and other information. Then feel free to visit my little BikeCliff website where I've been collecting the wisdom of this generous community. Don't forget, we like pictures! Not you, your bike!

Thanks for joining us. Keep us informed.

Thank you for your indulgence,

BassCliff

[hiroyakamotosan]

The "smoke" you're seeing is almost certainly the crankcase vapours, which are generated when the engine is running.

The breather tube on the top of GS motors is a method by which these vapours are recirculated into the airbox. These crankcase gases often contain significant amounts of unburned fuel and water vapour. This explains why the "smoke" has a smell of gasoline.

Suzuki designed it this way mainly as an anti-pollution device.

It seems likely that your breather tube is not sealing properly, which is why you're seeing this gasoline-smelling "smoke".

Maybe you could replace that as a first step and see whether there is any improvement.

Well that might explain a lot as the bike doesn't have the stock air cleaner on it. A previous owner along the way has put the little pod style filters on it and had the breather tube tucked away under the gas tank. If what you say is true about the unburned fuel and water vapor, then unless I get the stock airbox on it, there isn't much I can do about the wisps of gas/water vapor coming from the breather tube.

But at the same time, it is not as big of a problem as I thought. If it's just vapor that would normally be recirculated into the engine, it's not really an actual mechanical problem with the motor, just a question of getting that stuff recirculated, does that sound right?

[Guest]

WElcome to GSR,

You can run a hose back under the seat to the tail and put a round crank case filter on the end. Performance automotive shops have them and if you want to pay way to much Harley shops.

They look a little like this http://pingelonline.com/crankcase_vent_filters.htm