HI!

I have a 2001 Cbr 600 that was used two years ago, started last season, and sold last night, before developing such an issue i bought it back from the buyer.

The bike ran great at idle and revving the engine under no-load, revved freely and sounded great.

But when the new owner got down the block the bike stalled, and began running rough, the new owner checked the oil level, overfilled it, eventually came back, we drained the oil to the correct level again, eventually the bike would idle fine again. no smoke from exhaust, but when given some rpm would begin to smoke white, missfire, burning oil ect, and stall when returning to idle. We pulled it into the garage, took the intake off, and when moving the (throttle bodies???) 3 out of 4 cylinders were puffing smoke out, and cylinder 3 had a ton of unburnt oil in it. We theorize that the crankcase is pressurizing and pushing too much oil / vapors into the intake, there was even oil mist on the bottom side of the fuel tank.

The oil light starts blinking on when the bike runs rough, but did not show up at all when i was running it and checking the bike over in place. And goes away when the bike decides to idle well, when the exhaust smoke starts, the oil light also starts.

Is there any thing that could cause this that doesn't involve a rebuild?
I am into cars quite a lot but haven't worked on sport bikes at all, so any advice as to things to check and an order of operations would be welcome.
I have access to a fairly well equipped garage so i should be able to do the things recommended to me, thanks!

 

What is history of this bike?
When was last time if was working perfectly?
What kind of oil have you been using?

Do compression-test 1st.

Rings might not be sealing, which leads to blow-by that goes out crankcase-breather into airbox and back down onto throttle-bodies.

Can also drop borescope camera down plug holes and see what combustion-chamber looks like.

 

You sold the bike to a new owner, who overfilled the oil, and you bought it back?!?

You've at least got oil over the plugs and throughout the air intake, could be as bad as bent piston rods. Might even have a oil pump failure due to pressure. Lots of things can go bad if you overfill the oil.

Clean up the intakes, plugs, cylinders etc as best you can - drain the oil and see if there's any metal in it. There should be NO oil in or above the cylinders.

 

Bought the bike, rough around the edges had been dropped by previous owner, bought to ride while learning without fear of scratching the paint, drove for two summers with zero issues.

Sat unused for the last two seasons aside from an idle once last season, and firing it up to check all the wiring this season.

Fired right up and seemed fine

It was not driven on the street for two years until the new owner drove it down the block and started having missfires, stalling.

Bike idled great and revved fine while sitting in place before that.

Compression test shows 155 across all cylinders,

Intake isn't full of oil, however the cylinders certainly had some in them, spark plugs were wet.

i also tested the (crankcase solenoid???) and was not able to make it actuate, wondering if someone could explain how the crankcase vent system works on this bike, as i am leaning towards that being an issue.

Theoretically the crankcase is pressurizing and pushing oil past the rings?

As there is no sign of oil in any of the breather hoses or in the intake...

 

Crankcase vents to airbox to depressurize crankcase. Vacuum in crankcase lowers pumping losses (bottom of pistons has to push less air around). If you have oil coming out of crankcase vent, you've got some engine troubles.

Also 155psi is way, way too low. Should be +200psi! Drip 1-2cc oil into spark-plug holes and try again. You're holding WOT when cranking for compression-test?