Gixxerthou Posted August 1, 2009 Report Share Posted August 1, 2009 Told a guy selling me my shims to me today about the amount I've had to change, and he said its down to modern fuels... Does anyone know what he meant buy it? Do modern fuels burn hotter and therefore wear out your valve seats faster, making the valves close up to the cam quicker? or is it another reason? Yours confused, Ripley Link to comment Share on other sites More sharing options...
lorenzo Posted August 1, 2009 Report Share Posted August 1, 2009 unleaded burns hotter than 4*, yes, but on an aluminium head with valve inserts this shouldn't be a problem at all. Link to comment Share on other sites More sharing options...
gregtrx Posted August 1, 2009 Report Share Posted August 1, 2009 Is it cos the bikes run leaner to get through emissions regs? Link to comment Share on other sites More sharing options...
Mr.Pigdog Posted August 1, 2009 Report Share Posted August 1, 2009 I was always led to believe shims are required as the valve stretches as a result of high revs rather than valve seat wear.Just wanted to throw that in there-who knows for sure? Link to comment Share on other sites More sharing options...
ronenige Posted August 2, 2009 Report Share Posted August 2, 2009 The older fuels with lead in them tended to be kinder to the valve seats , some of the mid 80's kwak's used to hammer the valve seats into the head and eventually run out of valve adjustment if run on unleaded altho' they were supposed to be able to run on it . Shouldn't be a problem with modern bikes and materials , i've seen several motors do over 100k miles and never need any valve adjustment Link to comment Share on other sites More sharing options...
fran9r Posted August 2, 2009 Report Share Posted August 2, 2009 What bike was it? CRFs have a reputation... Link to comment Share on other sites More sharing options...
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