Noob

Greetings,
I have been lurking on this forum for a year or so, but this is my first post.
I have a 1970 Commando 750. It has a central oil tank, but the gas tank is steel. It has been painted black, and it's my understanding that there were no black bikes from 1970. I can see some yellow on the inside of the side covers. I assume that was the original color. It also has a front disk brake. I think the forks are from 1973. I have had it for about a year and a half, but only recently got it started. There are several issues that need to be sorted out. One of them is that there is what appears to be a fitting on the front of the oil tank about a third of the way up from the bottom. It looks like a DPO beat it off with a cold chisel. Today when I started the bike oil was spurting out of this fitting. I have started it several times before and it has not done this. I have no idea what it is for. I stuck a scribe in it and it seemed to bottom out about two inches in. Any ideas would be very much appreciated.
Thanks in advance,
Dan Fordice, Shoreline, WA

If I'm understanding your description correctly, you are right about a piece being chiseled off. That's where a metallic stem on the oil tank was attached to a hose that ran to the back plate of the air filter cover. It was there to handle an overflow of oil and would puke excess oil into the air filter compartment, as I have found out after overfilling the engine oil and then running the motor. If you ever check your oil level, do it after running the engine, because otherwise the oil tends to collect in the crankase over time, and you get a false level reading. Running it circulates it through the system.

If you are able to make a fitting for it, you could attach a hose from the oil tank to the air filter fitting, assuming your original air filter is still on the bike, or to a small collection container to keep the bike tidy if the filter isn't there. If you do neither, then oil will come out of the hole when the level gets too high.

If that's not what you're talking about, then I don't know what it is.

That's what it is, allright.

I'd do the collection bottle idea, like race bikes use. it can be a pint bottle from brake fluid, zip-tied to the swingarm area.

The overflow sounds right. The oil was spurting out. There is no air filter, which is another issue to take care of. The original fitting was cut off flush with the oil tank so I'll have to see if I can clean it up and tap it for a tube of some kind. I think a check valve is also in the works. It seems to drain back into the sump very quickly.
Thanks for the help.