‘73 RT1-360 - 1st time on the road after 25 years.
Filled the oil tank to the top. Road on street as a shake down, nothing stupid. 30 mph 3rd and 4th gear. After about 5 miles, I checked the oil and found it was down some. Ending up putting a full qt in it. At this rate I’d have to carry a case with me. Did not notice any excessive smoke or anything. This isn’t normal, is it?

I would consider pulling the oil pump cover and making sure its not squirting into the cavity or leaking to ground, cracked
delivery tube, something odd. Check pump adjustment, measure output.

MarkT on this site I believe posted a chart of the expected output.

Found this on the 250 and 350a as a reference, post 4:
yamaha-enduros.com/index.php/forums/74-7...t-volume-specs#95550

How long should a quart of oil last?

Depends on how you ride but I'd say after roughly two full tanks of gas it's time to check and top off the oil tank... and it should take less than a quart to top off.

You might have the seal in the clutch cover leaking... check the trans oil level and see if it's overfull and/or dyed the color of your Autolube oil (if you are using dyed oil)

A pint bottle lasts me quite a bit? I'm thinking 4+ full tanks before I'm in the "bottom of the sight glass window" range. I'm with pabdt pull the cover, you might find the oil pump cavity full of oil from leaking pump seals. My current DT1 leaks from the "white rotating wheel's" shaft seal, which does wick out of the cavity past the cover onto the ground after riding.

HVCcycle.net sells a pretty nice rebuild kit if you're up to it. Otherwise rely on DEET on this forum, he's a magician with the oil pumps.

That is a little worrisome as the overflow tube is really the vent tube! Plugged up and no flow to the pump! I have an RT3 and there is no reason for oil to flow out of the vent on the tank. Someone may suspect a problem with the pump trying to pressurize your tank?

I checked the transmission level. Nothing suspicious there. No oil underneath. Weather’s to bad to pull the covers but as soon as things clear up, I’ll check.

Pretty sure that is related to atmospheric pressure, but I'm not bright enough to explain it properly!

Gr8auntiepat's RD200DX does the same, as does one of those pump type soap dispensers in our spare loo (that did have be nonplussed for a while though! ).

On the later models Yamaha ran the vent tube up along the frame under the gas tank so it's a few inches higher than the tank.