[FLASHLIGHTBOY]

hello... I had this problem with a motor as well... torn it down could not see any thing.. switch the complete motor from a brand new unit... ( I am a dealer so I can do that )... and it did the same thing... I was stumped.. then I realized I used the carb that was on the one that was making the noise on start up,,.. only when you tried to start it.... the carb was switched with the one that was on the other atv... perfect... the throttle plunger was set to high allowing it to get too much fuel on start up... so I lower the plunger .. ( the one on the cable).. so it would not draw as much fuel on start up... ( PERFECT.. )
WHEN you try to start it and give it throttle as some require it... it would over fuel and KNOCK on start up,... like pre-ignition.. stupid problem.. drove me nuts.. so lower you throttle setting.. and DO NOT GIVE IT FUEL ON START UP.... I am sure lots of atvs have this problem.. I now notice this on some atvs. as people twist the fuel trying to start and it over fuels the motor.. and either you flood the carb and sparkplug... or it knocks too much fuel in motor.. try it and let me know..