1999 Yamaha 80 4 stroke top plug fouls

superdave1953

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Joined
Jun 24, 2006
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4
Sorry, I hit tab before I finished the last post. The top plug fouls after 10 min. I was told the thermostat may be stuck open and not heating up the motor. I replaced it along with the plugs, after 10 min of idleing it fouls again. Checked the top choke, had vac gauge put on the carbs, all is OK, now I am told it may be the head gasket, compression test, 150 top, 125 others. not sure why the top is higher than the others. Any clues on what the problem may be? thanks
 
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