Small Engines (Lawn Mowers, etc.): whats wrong with my mx 470 ski doo, carburetor issues, correct heat

Question
i have a 1985 ski-doo mx 470 and it keeps fouling plugs. It runs good for about 20 min after i replace them but then it fouls them. what do u think i should do.   i thought coils but i m not sure. what do u think it is

thanks
 jason  

Answer
Several things can be causing this.  The first thing you should verify is that you have the correct heat range of plugs.  You haven't said what the plugs are fouled with.  If they are fuel fouled, you need to make sure you have no carburetor issues (clean, correctly adjusted, etc).  Another problem can be with the fuel pump leaking fuel in to the crankcase through the impulse hose/passage.  If the plugs are oil fouled, you will need to make sure you are getting the correct mix of fuel/oil.  If it has oil injection, there is a setting for the oil pump stroke.  This adjustment is made with the cable and you'll need to contact a dealer to get the correct setting.  If you have to mix the fuel/oil yourself, I recommend you follow the oil manufacturer's recommendations.  The equipment manufacturers always assume the worst oil will be used and recommend a ratio that is very rich.  Hope this helps.