AC DVX 90 Rich at Wide Open Throttle WOT

[Twilight228]

Good Morning All!,

After a significant amount of reading and tinkering, I'm stumped.  We have a pair of Arctic Cat DVX 90s (4-stroke), and one of them runs very rich at wide open throttle.  I've cleaned the carb (which was installed new  last year), verified the main jet (80) to be per the original spec, installed a new air filter, tried a hotter spark plug (CR6HSA), and adjusted the valves (tightened a modest 0.0005" but improved starting).  The hotter spark plug may have help just a bit, but not appreciably.

Just for fun, I swapped the CDI between machines, and that didn't help either.

Fouling plugs very quickly, but not to the point the machine will not run or start.  [black instantly]

Logically, I assume I'm revving out, but the other machine doesn't "stumble/blubber" anything like this one.

Should I try a smaller main jet?

Any ideas you guys may have would be much appreciated.

Thanks in advance everyone.

[Frank Angerano]

Quick question, have you checked the fuel pump to see if the diaphragm is ok and not broken to see that  fuel is not back flowing into the carburetor causing a rich condition?

[Twilight228]

Update/correction.  Swapped everything around today again between the two quads, and the stumbling is dramatically less notable with a CDI swap.  

New Question:  I assume I should replace with an OEM CDI, but is there a better CDI made by an aftermarket manufacturer?

Thanks again guys!

[Frank Angerano]

Ive honestly not seen anything better then an oem cdi.   
Aftermarket ones are garbage unless its a performance one and thats double the cost of an oem.  

[Twilight228]

Is there a particular performance CDI you like Frank?

[Frank Angerano]

Nope honestly i look on eBay for a used oem if its in good condition