350F dies when I give it gas

[Evil August]

How exactly do I do a leak down test?

[crazypj]

You take it to a shop and pay 30 mins labour, (unless you want to buy compression and leak down testers?)

[Sonreir]

They make specific kits available, but mainly the idea is to get an air fitting that screws into your spark plug hole and then you use your air compressor to pressurize it up to 100 PSI or so.  Obviously, that can only be done with the valves in the shut positions and so rotating your crankshaft as you go from cylinder to cylinder will be necessary.

After the cylinder is pressurized, you listen for leaks.  Air sounds coming from the exhaust, means your exhaust valve is leaking.  Air sound coming from the intake means intake valve is the problem.  Listening through the oil filler cap usually means leaky piston rings, but can also be the head gasket.  The air will definitely leak out (no cylinder is completely air tight) but it's generally considered healthy when the air is leaking slow enough that you can't really hear is escaping.

Provided the leak down test checks out, then you know the oil problem is with your valve guides.  I can't remember if you said you already did a compression test, but most of the time a good compression test means a good leak down test.  A leak down test is just a better way to pinpoint problems.

[Sonreir]

You take it to a shop and pay 30 mins labour, (unless you want to buy compression and leak down testers?)

Or that. 

[crazypj]

I would re check timing is correct and advancing properly then re-do carbs.
Bikes are tolerant of a massive amount of abuse and an inline 4 will run on 2 or 3 cylinders
You do have plug caps in correct order?
I think left coil goes to 1-4, right to 2-3
Don't know how many times I've seen left coil on 1-2 and right on 3-4
 They could be fitted different but even so, one coil does 'outside' cylinders and one does 'inside'

[Evil August]

What would cause the engine to rev when I'm not touching throttle or choke?

[surffly]

What would cause the engine to rev when I'm not touching throttle or choke?

many things

[Evil August]

What if say, I found one of the lock nuts loose on a synchronization screw that was vibrating about? Yes?

[Evil August]

And yes the plug caps are correct. One inside (2,3) and one outside (1,4).

[Sonreir]

Possible, but unlikely.  Most common culprit is air leaks.  The condition is called a "hunting idle" if you feel like Googling it.

[Evil August]

Where could I be getting air leaks besides the intake manifolds? They are new and I don't get any change when I check with starting fluid.

[Sonreir]

The most common spot is the intake manifolds but leaks are also possible at the head gasket (compression check should identify this) and at the valve seals.

[crazypj]

What if say, I found one of the lock nuts loose on a synchronization screw that was vibrating about? Yes?

 If carb sync is off, it causes all sorts of issues.
You could be running on 3~4 cylinders, load one up or lean one off and it drops out then cuts in again
 Get carbs back off and 'bench sync' so all slides are at the same level when throttle wheel is just slightly moved.
At least that will give you a starting position

[Evil August]

Tried some #98 main jets. Didn't help. Going back to stock #75s and go from there. It actually flooded so bad it pissed out the overflows with the #98s.

[Swapmeet Louie]

its lean!