Carb bulbs - do you mean primer bulb or carb bowel?
To add to the above. With one of these engines, I've owned 2 v4 crossflows over many years personally and am about to commission a 3rd, here's my cold start steps.
1. launch boat
2. trim engine down
3. pump primer bulb until it's firm, not until fuel blows out the carbs, but not all wimpy either - you can hear the sound of the fuel going up, air coming out, when you do this
4. I push the choke/enricher in while cranking and while running the idle lever up and down a bit (not all the way up, just the bottom 50% of travel) - an engine running decently, pops right off within a few seconds of doing this, you then push that high idle lever down so it doesn't race off, you might need to bump or briefly hold the choke for the first 10 seconds of running as it finds it's pace (but too much choke will stall it) and shortly after you can push the idle lever full down. At that point I let it run, and I park the truck/trailer, and it will be running & happy when I return.
Now if it doesn't fire up under the circumstances in step #4, I get more aggressive with the lever, try with/without the choke, pump the primer bulb again, eventually I will check the water separating filter (which never has water in it on my boats but is worth a shot) etc. etc.. And I make a mental note something is goofed up with the carbs, because that is about what it always is when something like this is noted.
Most of the time, provided you are using the choke right and it works, the idle lever, the carb bowls have fuel in them at the time, etc - if you are starting hard it's carbs. And when it's not carbs it's there isn't fuel (could be a liquid still, but not just fuel) in the carbs.
Once these things are warm, a bump of the key and they should fire right up consistently.
Compression, lots of things, could cause hard starting. But most of those things come with other symptoms when running.
