Topic: Breather Tube broke. Oil Everywhere... How to flush carbs?

[lajollacb550]

Hello.  Came across this forum earlier today when searching for solutions.  Looks like a good group of owners.  Hope someone can help me out with a few easy questions I can't find answers for.  I recently picked up a rebuilt 74 CB550 and it was running great until the the breather tube broke.  I was on a long roadtrip and was forced to ride it about 80 miles (adding oil every 10 or so) to attend a critical meeting.  There is oil all over the back of the engine, frame, tire, etc.  Luckily I didn't go down due to the oil on the tire.  Anyways...  the bike is back home now and ready to have the breather hose replaced.  My questions are the following:

1.  There is oil in the air filter, so I'm assuming the carbs are full of oil too.  Do I need to take off the carbs and clean them out, or can I get by with just running them as they are and let the gas clean them out naturally?  Probably a stupid question, but the carbs were cleaned/checked less than 500 miles ago!

2.  Any recommendations for removing the oil from the sides of the back tire?  (it's an almost-new Metzler, so would rather save it than buy another tire)  Would engine degreaser work?

3.  Is there anything else I should do, besides replace the air filter with a new one?

4.  Are there any common issues (besides old age!) that might cause the breather tube to break?  I was doing between 80-90 mph when it happened, so I'm guessing it was being pushed too hard.  Boo for trying to keep up with traffic on the 5 through Camp Pendleton.

Any/all help is VERY appreciated!  I'm a newbie with bikes, but am learning more each day.  Cheers.

[jeepster]

Hey. Welcome to the forum. Nice to see that your introduction to the eccentricities of SOHCs didn't end up with your oily,fiery death.  

Sounds to me like an old, rotten hose. Some air filters are oiled. I can't really think of a way for the oil to pass backwards through the carbs all the way into your airbox...especially if you were going 80-90...

Take my advice with a grain of salt though as I am still a noob too. I'm sure someone more sage than I will chime in and clarify.

[Bodi]

Sounds weird. The breather tube should exhaust a smallish amount of stinky crankcase blowby gas, oil shouldn't be involved much at all. This is the tube from the top of the engine to the airbox, yes?
There's a filter element in the airbox that's supposed to soak up any oil droplets carried out with the blowby gas from the hose. It should be cleaned every now and then (monthly??) and holds maybe three tablespoons of oil maximum. So... normal operation doesn't blow much oil out that hose.
The hose should be wide open to the airbox, letting the engine ingest the blowby gas and send it eventually out the exhaust, basically so the stink doesn't waft up in your face at stoplights. Whatever blew out on your engine and tire is not at all normal, and would have blown into the engine otherwise. It's telling you it has a problem. Excess blowby as a rule means worn rings and/or cylinder bores. Extremely worn exhaust valve guides can give a lot of breather vent gas too. The oil is a byproduct of the excess blowby: oil droplets are always blowing around inside the crankcase and naturally some come along with the blowby. There's a bit of a labyrinth separator in the top of the engine that will coalesce the droplets out at normal blowby flow but if you're really blasting gas out it doesn't work.
High RPM and high throttle gives you the most blowby but 80mph on a 550 isn't a big deal, it should manage that all day (maybe not uphill...). I would check compression and probably fix the engine before going on any long trips. Reconnecting the breather hose will stop the oil spraying around but it will still be blowing into the airbox. If you had to top up the oil 8 times in 80 miles you will have several problems. The bike will smoke like a Trabant, the air filter will get soaked and clogged, the plugs will foul, and the engine will run dry of oil pretty quickly... hopefully your oil pressure light works and you notice it coming on.