Rancher 420 fouling plugs?

[motoz/HMF]

From the net.

They should scan it with the HDS, check for codes and if none found do a ECM reset. Then let it idle for 10 or 15 minutes. Also, if nothing is found during the HDS scan, remove the seat, turn on the key and listen for a buzz on top of the throttle body to see if the IACS is cycling.
Honda did have a certain vin range number that had to be checked for valve clearance when they were shipped out. I have found some tight when units are scheduled in for a 20 hour check.
If the unit still fouls plugs after all these checks, remove the IACS and clean it's slide and passage, reinstall and reset the ECU