The blowby pressuring up the crankcase at the same time piston speeds are high and oil pressure is maxed out, creating the oil vapor in the air,,,and the crankcase pressure along with the amount of oil in the air causes oil to get past the scrubby like wadding.. And hopefully someone will run a test. I'd be happier with loss from blowby than burning it.
And I don't know why...

I try not to get over 65. It just sounds/feels like it's going to explode at any second!

That oil looked pretty thin!

Old Rider, you've probably done it, but I would check out the vent tubing, and maybe even pull the oil fill plug and blow into it to see how well it's working.
Or, you've got a Lot of blowby,

sometimes mine sounds strained at 70, sometimes it sounds like it's humming happily away
seems happiest when it's cool out
akso, have now determined to run her up to 75 in 3rd, just to see what that sounds like
what's top speed (or close to it) in 2nd?
one thing about the rebel was, it was just too limited by intake to over rev in any gear under load, just pin her ears back and shift when she quit pulling  

ok so 50 as a safe bet for a short time  
thanks for the chart, it's been posted here before but darned if I could FIND the fool thing

Serowbot wrote on 11/03/15 at 21:50:22:


Speaking from experience?  

Mine both burn it. The oil fumes do get sucked back into the engine via the carburetor, at least most of them. I've run out (2 full quarts of 10W40 synthetic) in under 300 miles, mostly on old U.S. highways, Mississippi/Tennessee summer heat with the 98. That engine was still oil tight and had a capped puke tube, so the engine had to have burned off the oil during the combustion process.

The 03 has so many leaks I plan to top it up every ride, often during the ride. Sometimes more than once if we're riding 60+ for extended periods. If I could still find 1970s surplus Cessna 60wt cheap, that would be in the bike. Leaks like an old Benneville, and has the same Lucas electrical gremlins.