is there a formula to set a carb after muffler mods?

[kf_tree]

on a stock saw the carb needs to be adjusted to richen the mix after a muffler mod. is there a formula useing a tach?

lets say a 395 has a max rpm of 12,500 and stock the saw is set at 12,000 . so now with a muffler mod should i kick it down to 11,500?

thanks

 

[njforestfire]

IMO - it's where you want to set it. I would think you would try it in some wood and adjust accordingly. I also wouldn't think that you would need to turn it down just because it's modded.

 

[tony marks]

i would agree. if anything id think it would hold stronger at higher rpm . at least thats how it is with my saws modified by dan and dave. if somebody modified it for u . let him set it,, as he knows whats optimum for the saw if he modified it. at least u would hope so.good luck.
ps if all u did was open it up ,id just adjust it for strongst cut.i do these adjustments while putting the saw in heavy cut. be careful not to get it too lean.if shes too lean it usually will break dn under heavy pull if set to lean. at least that what the ones i opened up did..id hope so as if she cuts strong ,when set to lean ,shes also likely to sieze.. jmo

 

[ErrolC]

The higher the tune..the more sensitive the engine will be to variations in air temperature, density & humidity..this will vary day by day..and throughout the same day and to get the best performance from you saws engine you should adjust it accordingly..just cause the book says it should peak at 12500..doesn't mean your saw will..it could be better, or worse..the revs are dependent on the engine port timing/compression ratio/and capacity to breath as well as its efficiency in its ability to burn all the fuel mix at the right moment each revolution...thats the basics anyway..the mixure needs to be adjusted according not to the volume of air, but the weight of air passing through the carb..the optimum being about 14:1..14lbs of air to 1 lb of fuel..some days are hot and dry and the air feels thin..others are hot and muggy/humid & heavy (good power days)..cold and damp (misty mornings)..it goes on

 

[ErrolC]

P.S. always do your tuning when the engine is good and hot