Only 2 things can cause this.oil starvation (on a four stroke),or excessivly weak air fuel mixture.Check air filter and all carb to engine gasket's for leaks/security of fasteners.Take out your spark plug and check the colour of the electrode end,it should be the colour of a rich tea biccy.If its grey and shiney u've got carb problems.
caine
August 2008
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