I have a '99 400 Arctic Cat. I love it! Lately, the plug has been fouling and it has been blowing black smoke. Put a new plug, ran good for a short while and then back to black smoke. Tried adjusting the idle speed, my hubby took the carb apart to check for trash, no trash. Anyone else have this problem or can give me an idea of what is wrong or what to check next? Thanks in advance.

 

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Welcome to this forum.

The majority of fouling plug reasons are improperly adjusted carb, extremely dirty air filter (which changes its airflow), plugged pipe (which changes its airflow) or something mechanical. Such as worn valves, improperly set valves or worn rings / piston.

How many miles / KMs on your AC??? Does your AC burn oil? Does it smoke more during start up or does it smoke all the time? For visual smoke and burning oil, it could be worn rings or worn valves.

If possible, do a piston / engine PSI test and compare against normal operating range. This will help determine if worn rings / piston. For the PSI tool I use, surf:

http://community.webshots.com/photo/...83728005iTIPES
http://community.webshots.com/photo/...82885163LcpoBq


Hope this helps....

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Is your choke working properly? If it is stuck on alittle it will also foul yor plug....

 

I would wager that since it was working fine and now isn't that you have gotten a dirty air filter. If not the carb has got dirt in it and needs a rebuild. Of course check the filter first.

 

hamlin, dirty air filter most likely the problem, choke could be sticking but would most likely flood out quicker. Unless dirt in carb is holding needle open that would not cause rich condition. Dirt would cause lean condition by blocking off jets. If these are OK valves could be out of adjustment. Bear is right, check the air filter, easy things first.

 

Thank ya'll for all the info on what to check. We will be working on it as soon as we get some free time.