Hollow rattle, and a pop

I just replaced my needle and seat on #1 carb and I know I was running
rich last season so I turned my mixture screws in the with of a nickel
like Rickomatic suggested. I might try turning them back out and see what happens

 

You can be Lean and still Carbon-up if the Valve Seals are leaking or the Rings are letting Oil get by the Oil Control Ring.

The Lean Mixture looks for anything it can find as Fuel and burns the Oil leaking down from the Valves and the sheen on the Cylinder Walls left during the Intake stroke.

 

WE HOPE THAT THIS NOTTHE CASE. SOUNDS LIKE A COMPLETE REBUILD

 

can all of this happen within 25k miles

 

Yes, I certainly hope that isn't the case.

Found out why the engine sounds like a lawn mower; only running on two cylinders.. Here's the strange part: Cylinders 2 & 4 aren't firing. The ignition coils power 2 & 3, and 1 & 4, respectively, so I'm not sure why each ignition coil would only be firing half its load.

Plugs are brand new, carbs appear to be tuned (I imagine a lack of spark wouldn't affect this), and all fuel mixture screws are roughly 4 full rotations out (DynoJet).

 

Ok, time for a status update. Last night I:

-Swapped around the plugs
-Swapped plug caps between 1 & 4, and 2 & 3
-Redirected the spark plug cable from the coil to cylinder 1, over to cylinder 4
-clipped 1/2" off each of the spark plug cables

No matter what I did, cylinders 2 & 4 are not firing. Headers are only luke warm on those cylinders. Plugs are clean and wet (gasoline). I tested them, and I am getting spark at all plugs. The resistance is a bit high on the plug caps (one is at 12K ohms), but all the plugs/caps/wires fire on cylinders 1 & 3.

I cleaned the carbs well a few weeks ago, but he bike hasn't run properly yet this year. Floats to high, maybe? My carb drain plugs are fused to the bowls, so it's difficult for me to tell..