breather

[metalman]

Hi All:

I have a 1988 k75S I dearly love. While cleaning it this morning I noticed a thin rubber tube running along the rear swing arm (a breather?) had become disconnected. I wonder what the end was attached to and how I would go about reconnecting it.

Thanks,
metalman

[BuddingGeezer]

Battery or fuel tank overflow. Some Ks have a small cup for the fuel overflow to drip into, still has a tube though.

Ralph Sims

[amiles]

Usually on a lead acid motorcycle battery somewhere near the joint between the battery top and sides on one end there is a nipple that the battery breather/overflow tube attaches to. This should be easy to determine hopefully making your diagnosis simple.

[35634]

Probably the fuel overflow or vent. Not too serious, but you'll probably have to remove
the tank to re-attach it.

[breyfogle]

While cleaning it this morning I noticed a thin rubber tube running along the rear swing arm (a breather?) had become disconnected. I wonder what the end was attached to and how I would go about reconnecting it.

Aaahhh, the only "thin rubber tube" that normally runs along the swingarm is the electrical wiring going to the speedo sensor on the Final Drive. If it's "disconnected", - - - it broke.

[Ted]

Not too serious

Having had my trusty old K75S erupt in flames while zipping up an onramp to the Spaulding Highway I will heartily disagree :)

It is easy to check, just pop up the tank and the little plastic cup (aka air accumulator) is zip-tied on the frame member under the rear of the tank on the right. It is #5 on this graphic (and #4 is I believe the drain tube in question):
http://www.maxbmwmotorcycles.com/fiche/DiagramsMid/B0000406.png

[Kayseventyfive]

Having had my trusty old K75S erupt in flames ......

Boy, you sure know how to scare a guy! :uhoh

What do you think was hot enough or sparky enough to ignite the overflow fuel?
Was this just after refueling?

.

[metalman]

It looks like the breather for the battery is routed down in front of the swing arm, so I think the likely source is the fuel tank overflow. I'm going to pull the tank tomorrow to check the fuel tank overflow. Thanks one and all for your helpful suggestions.

[Ted]

Was this just after refueling?

You bet...

Whole story - August, 1996... I had owned this K75S for about 8 months when this happened. I was on my first day of my first long (ie 2 weeks+) motorcycle trip and had zipped up the east coast from DC with no real destination in mind other than maybe Islesboro, Me or North Conway, NH, or in general just to be north of Boston by nightfall. I got to New Hampshire on I-95 and saw the sign for the Spaulding Highway. Now I had driven up and back from DC to Maine every summer and every Christmas since I was 16 (and been a passenger since I was an infant) and had always wondered about that road. So after about 5 seconds of deliberation I took the exit off I-95, then the first exit off the Spaulding Highway for Gas.

The clerk informed me that it was full-service only and so I let him pump the gas and went inside for some more water.

BIG mistake.

I left the station and as I wicked it up going up the long circular ramp I happened to look down and notice the whole side of the bike on fire. I stopped immediately and jumped off - I grabbed a handy bottle of water and doused the bike. I figured out a few weeks before that a 1-liter bottle of water will fit perfectly snug in between the tail and handle of the BMW hard cases so I kept one on each side - very lucky for me.

I sat there on the side of the road for a minute trying to digest what just happened when I guy named Barry on a Harley pulled up and asked if I was OK. I told him what happened and he suggested we unpack things a bit and take a look. We did just that, and after a few minutes it was apparent that:
1. The idiot at the gas station had filled the bike to overflow, all the way to the lip of the fill and then some.
2. I not only had no air accumulator, I had not tube or anything that would stop the tank from dumping overflow gas all over the engine of the bike.
3. Luckily, the only damage seemed to be a singed accessory socket wire (and a singed Aerostich leg...)

When I opened the gas cap I saw that it was filled to overflow so we siphoned off about a third of the tank into Barry's bike with a length of gas hose he had in his bag. When we popped up the tank to inspect for damage it spit a bit more gas from the rear nipple and it was apparent something (the air accumulator) was supposed to be there, and wasn't. We saw the only damage was the accessory socket wire so I taped it up with electrical tape I had in my cowl, then zip-tied my Harly friend's gas line to the tank nipple and ran it down the side and below the passenger footpeg.

Bike started right up as it always did and off I went, leaving the Spaulding Highway for another day and deciding to head to Maine instead.

Whole trip report is here:
http://www.verrill.com/tripreports/canada96/

I later installed the air accumulator and gas hose, total cost was around $10 and about 30 minutes time.

[Kayseventyfive]

Still curious about how the fuel ignited.

Looks like I will carry a water bottle ALL of the time instead of part of the time. :)

Thanks for the info.

[Ted]

Still curious about how the fuel ignited.

My guess at the time was the alternator.