oil tank eruption??

[snowbeard]

well I went out to the garage tonite to work on my regulator, and I found the oil cap off the tank, and oil all around the filler hole, dripping down the side, along the frame and a big splash to the side on the floor!?

I can't remember for sure if I had the oil cap off last night after my ride or not, but I'm pretty certain I didn't.  I also didn't tighten it excessively before my ride last night, so it may have shaken partially loose, then unscrewed itself the rest of the way from a backpressure into the oil tank?   whatever it did, it was pressure related, I see oil up onto the side of the seat and the frame above the tank as well, but the threds are fine, intact, nothing odd.  the cap was on the tranny just below the oil tank, right side up even.

so I guess I better check that breather, eh?  do you think this could be pressure building up and making my rocker covers weep oil at an alarming rate as well? (think slight pooling).

has anyone ever seen this before?

I posted about that on "that other forum", I hope people don't get territorial about that sort of thing, but here's the link.  http://www.britbike.com/ubb/noncgi/ultimatebb.php?/ubb/get_topic/f/10/t/007273.html

please excuse me if it's frowned upon in these parts to cross-post...

[fido]

There should be a breather pipe at the top of the oil tank so unless that is blocked the tank can't pressurise. The cap could well have vibrated loose on your ride. If it only has a fibre washer I suggest you replace this with a fairly thick O ring. The compression of the O ring works like a spring washer and helps prevent the cap from vibrating loose. If you had a problem with engine breathing there would be other symptoms such as major oil leaks. At this stage, until you are certain about the state of the mechanicals it would be wise to take off the cap now & again to look at the oil return flow. It you do this when you first start the engine you can check how long it takes for the returned oil to contain air bubbles. This will indicate how much oil has drained into the  crankcases. You always need to run the engine for a short time before topping up the oil in any case, to ensure all the oil is in the tank, not the engine.

[snowbeard]

yes, I rememered the breather later, but it is clear.

it must have been that I left it rather loose (relatively anyway) before the ride, and just got extra lucky it didn't fall off on the road!  maybe there was a pressure bubble backflow into the oil tank from some engine pressure, I do have a seeping leak around my rocker box gasket.

I will get a good oring, this one is a paper seal. thanks!!