oversize pistons/jetting

[ken007]

hi, on my 350lc the pistons are 2mm o/s, is there any rule of thumb about re-jetting or do you just start at standard and go from there?? thanks ken

[Jeram]

generally (but not always) going larger in capacity will increase your carb velocity and will therfore cause your bike to run rich... which is good and safe!

then you can work your way back from rich, to just right.

[ken007]

thanks jeram, its info like this which helps explain things a little bit more,,im finding it a bit complicated getting these carbs running perfect , but arent to far off the mark and am, cautiously on the rich side,

[Jeram]

no worries,

just so people understand the pricipal behind it, its all based on bernoulli's equations.



as you can see, velocity is squared, so it has a much greater influence on the equation than other parameters.
in essence: a larger piston = more suction in the carb = higher velocity in the carb = lower pressure in the carb = more suction of fuel from the carb bowl