cb350f73,

Have you checked inside the air cleaner for oil? If you've got oil in the air cleaner, you've got blowby past the rings. That pressurizes the crankcase and reverses the normal flow of "breathing" air for the crankcase. Oil vapor is carried into the intake and burned with the fuel. Because the amount of oil burned with each ignition is small, smoke is not apparent at the tailpipe. But, 3500 RPM equals 14,000 ignition events every minute, 1,120,000 ignitions on your daily commute. A lot of oil can be consumed over the course of a week without visual symptoms.

The fix? Rebuild the engine. If you can't afford the downtime, buy a long block and install it over a weekend. Then you can rebuild your original engine, pickle it, and stash it away for that day a decade or so from now when you will need it again.

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Mr. Shannon DeWolfe -- (I've taken to using Mr. because my name tends to mislead folks on the WWW. I am a 52 year old fat man ;-) -- KD5QBL