A mystery! '81 gs550mx oil loss

[Cipher]

hmmm some guy on here suggested that oil level shoul always be midpoint on the sight glass
Maybe the oil is ending up in your airbox

[Nessism]

20W-50 is a good grade for riding in hot weather. Going to a thinner oil will result in more oil loss.

Your method of measuring oil consumption is not ideal. You need to be checking the oil per the service manual's guidelines and over the course of more miles. Try topping up the oil to the top of the sight glass and then monitor the level until if falls to the bottom line of the sightglass, and then measure how much oil it takes to get back to full. You gotta keep track of the mileage too of course.

Unless you are leaking oil the consumption is not what you suspect.

[Cipher]

use the OEM suggested weight. An oil that is too heavy for the ambient temps will not be properly scraped by the rings and will get past and into the combustion chamber

But its would cost you an oil change to find out.
Also quit over filling too high youll get windage issue from oil being whipped by the crank and other moving bits.

[duaneage]

Check the drain hole for the starter. It's a small hole that allows water or oil to escape from the starter compartment.
I had a bad seal inside my starter that pumped a lot of oil out. I put some cotton in the hole and drove 5 miles. It was soaked.
It didn't leave any evidence on the engine really, leaked straight down. There is also a seal around the end of the starter that can leak too

[Big T]

I'd suspect the cam chain tensioner seal and gasket.

It would leak down the back of the engine and out the drain hole under the starter, as per Duane

Per Ed, only fill the oil to the top mark and see how much loss you have over 300km or so. Overfilling, as you are doing, is a guaranteed oil loss.

[Katmantoo]

I posted a reply but it seems to have disappeared! So.......
Please check my previous post regarding my method of measuring the oil loss. I am not overfilling. I clean the engine before each run and check it on return. There are no oil runs or drips anywhere and no oil under or on the rear of the bike. So the plot thickens.
I appreciate all the input.
Looks like new valve guide seals are worth trying. The alternative is carrying lots of oil and checking the level frequently!