Pressure under the valve covers?

So, I have an '84 VF700F that's new to me, and I'm working to get it running properly. I decided to check the valve tolerances and after doing so, I broke off one of the valve cover bolts. I thought, 'No big deal if it leaks a little oil out of the hole, I'll fix it later,' and I continued reassembling things. After firing it up, I noticed that it only wanted to run on choke, and it died with any throttle. Running lean, right? Also, I noticed a bit more than a small dribble out of the hole where the valve cover bolt goes, it was really throwing oil out...

Isn't that strange? Why would there be so much pressure under the valve cover? Is the whole motor out of timing?? I did a sanity check and pulled another bolt from the valve cover on the other head, and that one too is really puffing air out the top, as if it's TONS of blowby, but it does idle relatively okay, so I don't think so.

Anyway, I realize now that fixing that broken bolt is my new #1 priority. I ordered a replacement and some Grabit Pro Micro bolt extractors, hoping that I can get the broken part out without having to pull the whole cylinder head off. But now I want to do a compression test too! Why would there be so much pressure under the valve cover? Is there some counterintuitive design with the crankcase ventilation on these motors? Or does this behavior indicate some other issue?

 

Pressure? None, really, I wouldn't. A lot of moving parts bathed in oil throwing oil everywhere...likely.

 

I mean, just holding my hand over the hole where the bolt goes, it was puffing with serious force. From what I know about cars, that means SERIOUS blowby, but that wouldn't make any sense given that it seemed to be running on all 4... Valves should only be going up and down within their respective intake/exhaust runners and not making much of an impact on the pressure in around the cams, unless there's absolutely no valve stem seals left. That's why I'm thinking there's something else wrong, or else just something very quirky about these motors.

 

How can it 'idle ok' if the choke is required to keep it running? Sounds like carb circuits/jets plugged. If those valve cover bolts are the same as on a 500 they are shouldered & easily broken if the torque spec is exceeded.