Phantom oil loss!! Where is it going?

[JHawkins]

Well, I am at a point where my head scratching is creating a new Grand Canyon!

I put on about 900 miles this weekend - After about 500 miles I had lost 1 quart of oil, after the other 400 about 3/4 of a quart.

This bike has had a known valve cover leak that was just fixed. There are no other significant leaks that I can find. Valve cover and head look dry, filter cover is dry all over, base plug is dry. The only oily spot is the Cam Chain tensioner and it is very, very light and there is no sign of any amount of oil anywhere else.

The bike is running perfect, best it has ever run in fact. No smoke at all, even under heavy loads. I am stumped

I just ran out and did some checks on plugs as I wrote this:

1 - tan
2 - black
3 - tan
4 - tan

Compression dry:
1- 107
2-105
3 - 90
4 - 112

Compression oiled:
1 - 117
2 - 117
3 - 110
4 - 117

So, this doesn't tell a whole lot - obviously 3 has a problem, and 2 being black has a problem (I suspect the petcock, as it is not shutting off completely any more)

This still doesn't lead me to a quart of oil every 500 miles, if it was being burnt in #3 then I would think the plug would be oily.

[JHawkins]

hmmmm, 117, 117, 110, 117

when they showed 117 they were exactly in the same spot, I am wondering if there is a problem with my compression tester!

[JHawkins]

Yup, compression tester is fooked! found an old press on tester and was able to test both outside plugs at 140 - couldn't check the inner ones due to the tester. I will pick up a new one and check, but I am guessing the compression will be not so bad.

Soooooo, ... that still leaves me with mysteriously disappearing oil! and even less of an idea why!

[bwringer]

I do know you can burn a quart in 500 miles with little to no smoke.

I used to have a VW that was picky about oil level -- anything above halfway on the dipstick, and it would happily slurp it up and burn it off. Anywhere below halfway, and the oil level would stay the same until the next oil change. Never a hint of oil smoke.

With that said, the culprits could be the valve stem seals, the rings, or some condition causing excessive crankcase pressure, such as a blocked crankcase vent line. I'm sure others will have other ideas...

[GSstiny]

Judging by the wet compression readings, Id say its valve seals. Even though those numbers arent accurate because of the tester, the amount by which they change from a dry test to a wet test should be about the same. Since the numbers didnt rise a whole lot, all the fingers point to valve seals. You can burn oil without it showing up on the plugs or blue smoke. When mine was running (down for going on 6 weeks now :shock, I could count on it burning about 12 oz of oil every 1500 mi with never a hint of smoke.

[flyingace]

Yup, compression tester is fooked! found an old press on tester and was able to test both outside plugs at 140 - couldn't check the inner ones due to the tester. I will pick up a new one and check, but I am guessing the compression will be not so bad.

Soooooo, ... that still leaves me with mysteriously disappearing oil! and even less of an idea why!

You know, this very same thing happened to me. I bought a new screw-in compression tester and it read low and never over 120. I found an old tester and it read 20 points higher. Can't believe they allow anybody to sell such crap.

I'm losing oil too - probably more than quart/1000 miles. No smoke, no leaks and compression is pretty good. I also suspect the valve stem seals. Looks like my winter project.