Burning oil w/ decent compression?

[Joe Garfield]

I don't see much smoke when I start - either none, or hardly any.

[geol]

Valve stem oil seals are not meant to be 100 percent effective in stopping oil from going down the valve stems but allow a little for lube. When the valve stem oil seals wear they will allow a bit more than enough to lube and the little few extra drops of oil will settle in the combustion chamber to smoke when the bike first starts but generally becomes un-noticeable after the bike is running. If they are really leaky, the bike will puff a bit of oily smoke when you downshift. They will never account for the amount of oil lost by the OP. That prety much can only come about from a large and very noticeable leak or the oil scraping rings are either broken or just worn or the piston to cylinder spec is now much out of space of the pistons have been rocking and the bores oval. Just aren't any other reasons. You don't see a pool of oil? You will likely have to install oversize pistons and rings after having the cylinders bored.

[Buffalo Bill]

Walter Brennan is here.

HA! Exactly what I thought, Sons Of Will Sonnet.
But, I was just trying to say, if the damn engine is all good, it should not burn oil, the only oil loss should come from leaks.
Even with the leaks, I only had to top off the oil at the end of summer.

[AMK]

I have the infamous secondary drive auto fill on my '82. After about 400 miles I have to drain the secondary drive oil and replace it and my engine is about a quart low. I'll fix it after riding season.
It will leak out the breather tube and down through the mystery hole. But when it does it's obvious.
Have you looked at the secondary drive oil level lately?

[Joe Garfield]

That pretty much can only come about from a large and very noticeable leak or the oil scraping rings are either broken or just worn or the piston to cylinder spec is now much out of space of the pistons have been rocking and the bores oval. Just aren't any other reasons. You don't see a pool of oil?

Nope. I park the bike in my garage and would definitely notice. It did leave a few drips from the mystery hole leaks, but that's all gone. Wouldn't all that stuff about bad rings or roundness show up in compression test? Or maybe running just above the min spec is enough to say there's wear?

I wonder if it could be coming out from the oil pan gasket, but only when the bike is running? I'll have to get some pics of the underside of the bike, but for now I'm in and out running errands on the bike, and enjoying it too much to stop

Have you looked at the secondary drive oil level lately?

I changed the secondary drive oil about 500-750 miles ago. I didn't know or think about an 'auto fill' since my secondary and final drives use hypoid oil, so this shouldn't have any influence on motor oil...right?

[geol]

Last time I post in this thread. Oil (aka oil scraper) rings are intended to scrape the oil from the cylinder wall. They are thin and made for the purpose and they are shot, oil goes right by and you can have high oil consumption with no loss of compression. Unless you see a puddle of oil when parked, there are not a ton of explanations. As I said once, if the cylinder is now out of round or the piston to cylinder wall clearance is too large, you will have the same effect. Lots of oil use.

[Joe Garfield]

Thanks. I always thought the rings were for sealing, so I'm just trying to learn something here. Now I understand and agree that the symptoms are pointing toward worn rings.

[AMK]

I changed the secondary drive oil about 500-750 miles ago. I didn't know or think about an 'auto fill' since my secondary and final drives use hypoid oil, so this shouldn't have any influence on motor oil...right?

The "auto fill" is actually a leak in the seal between the transmission and secondary drive. When the engine oil fills the secondary drive it comes out of the vent hose that routes through the starter cavity and out the mystery hole.
But it only does it when it's moving and it runs out onto the exhaust pipes and usually soaks the kickstands.
At first I thought the po overfilled the secondary but 400 miles later I saw it dripping and removed the fill level screws and oil came out like i had overfilled it.
If you don't have oil on the floor I'd rule my suggestion out. It surely would drip.