FD620D (Conquest) spark plug help

[sparkola]

Ok I am riding along and everything is fine. See another guy with an Argo and stop to chat for about 15 mins. Go to start up again and Conquest starts and I hear what sounds like a rod knocking( or detonation). Rev it up a little and goes away for a sec and comes back. Limp it back to my truck and pull the rear spark plug. Center electrode is missing. Run to Farm and Fleet and pick up a couple of champion O.E. replacements and replace both( front one looked a little carboned up anyway) Ride for a little maybe 1/2 hour and start bogging again. Load her up on the truck and drive home. Tonight I pull that rear plug aagin and again the plugs center electrode is seperated from the stem and sorta like a little melted ball stuck to the arm electrode. Compression on that cylinder is 210 cold and 220 on the front. Any suggestions?

[sparkola]

Another thing I noticed is that the metal portion of the plug (where the socket grabs) looks dull and the ceramic insulation had some black rings around it that I could scrape off with a fingernail. Does this cylinder sound like its running lean( hot). Any suggestions would help.

[eightwheeler]

very common problem, i have FD Kawasaki in my Argo and 6 wheel JD Gator and they both spit plugs not sure why they just do and the one is rebuilt too??

[sparkola]

The plugs that came in it and I replaced with is Champion CJ14. Is there something better?

[maicolover]

Sounds like its running lean? What color are the plugs. I won't recommend Champion plugs! These engines like new plugs from time to time but Not from being melted or burnt! They normally foul out from running rich and idling around. Newer 620 engines have longer reach plugs BPR2ES in them. But i don't think they will work in older 620'S. So you need to be finding problem before it melts a piston! We run NGK's in ours, you could try Denso, Boosh or Autolites.

[sparkola]

Mine is a 97 and I read somewhere that it's the older shorter plug. Perhaps Rock Doctor can chime in here. Yes it is kind of odd that it would start doing this all of a sudden. Do you have a number for the appropriate short NGK plugs?