Only running on 3 cylinders

[LAB3]

It's probably the "resistor" that is inside the cap. They are a carbon block, and do go bad. You can unscrew the bit that snaps over the plug, remove the resistor, and put in a short bit of #12 or #14 copper wire. You would need to do this to all 4 caps to keep the bike running correctly.

Occam's Razor: Given an equal set of outcomes the simplest answer is best!

Don't know how many threads in various motorcycle repair forums that I've come across over the years where a "carb tuning problem" ends up being an old spark plug cap with infinite resistance.

[Monkymann2]

Update I ended up just buying some caps like some of you said and 1 started firing again now 2,3 are getting hot just not as hot as 1,4. Idles rough and sounds like it’s not all together. I checked the timing 2 months back but from what I know timing doesn’t just change. Not sure where to go from here because I feel like it can’t be the carbs because I have the 4 into 2 set up. Also on this setup the vacuum advance isn’t set up so That could be the issue.

[IanDMacDonald]

You're throwing too many variables at this, and it's not allowing you to count out any specific system. My best advice I can give you to go back to a "standard" setup. Standard airbox. Standard carbs. Then, start diagnosing. Do you have the carbs tuned correctly? Can't get it to run right to get the carbs running? Then, assume it's electrical. "To measure is to know". Start running diagnostics on your distributor system, starting with your timing advance. Are the wires good? After that, check your coils. Primary & secondary resistance. Voltage source at the coils? If not, do a coil relay mod. You only need to replace the coils if they're bad. Dyna DC-1's are what I run. These bikes are stupid-easy to diagnose, as there is nothing to them. Hell, someone even figured-out the wizardry to the internals of the RLU and self-canceling relay.