Advice on troubleshooting oil burning/leakage

[Boellster]

Hi guys! I'm posting this as an attempt to sort my thoughts a little regarding an oil problem on my bike and to try to figure out if its something I can repair myself.

Problem:
My bike is leaking/burning alot of oil. After about 60km of riding I have to top up about 1-2 deciliters of oil. I notice it because the oil pressure light starts to flicker when gearing down, stopping and idling (never when driving at constant speed).

Background/details:
The bike is a CB750F -81 with a CB1100F -83 (SC11E) engine, mileage unknown (I suppose  that the SC11E is similar to the 750 DOHC engine mechanically). I use the original airbox but have removed the crankcase breather canister and replaced it with a small pod-like air filter that connects to both the outgoing air hoses through a T-cross. I have also disconnected the tacho cable and plugged the socket (small leak here). Otherwise no visible oil leaks and no dripping on the floor when parked. Some white smoke comes out when starting but I can't tell if its from burnt oil or something else (steam?). I normally use 10-40w semi-synthetic oil.

Question:
How to approach this problem and how to go about with the trouble shooting. I rule out electrical problems with the indicator light since the oil is actually vanishing (the oil dip looks dry when I top up). I've read that valve seals can dry up and start leaking oil into the cylinders. Should I start here? Will the spark plugs tell me something, if so what should I look for? If I tap out some oil, could looking at it tell me something?

Dont know if this is relevant but recently the engine started leaking oil through the valve cover gasket while I was out riding. When investigating it turned out that most of the bolts holding the valve cover were loose and couldnt be tightened due to broken threads. Put helicoils in all 8 holes, fitted a new rubber gasket, new grommets for the bolts and tightened carefully. Now, about 300km later I notice that the visible part of a couple of the grommets look torn. But no visible leaks from the new gasket or bolts.

Maybe a longshot, but could the broken threads come from too high oil pressure and due to the high pressure, oil is entering the cylinders? In that case, could it be the breather hose filter being insufficient/clogged? Sounds unlikely to me as I guess the filter would have popped before the valve cover...

Of course I could hand the bike in to a professional to have it fixed but I'd like to have a go at it myself first as I am curious and eager to learn more about the internals of the DOHC engine ;)

Thanks in advance!

//Boellster

[TOOLS1]

With the amount of oil you are losing, you should be able to see where it is leaking from. I would go to the car wash, and hose it down, then spray it with athletes foot spray that has powder in it. Then ride it a few blocks, and look it over. The powder will show any leaks. As for too much oil pressure, well it would not really be oil pressure, but crankcase pressure, and your little breather could be doing it.
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