1: Does a 160 main in the BSR Stock 42mm have the same flow rate as the 160 main in the HSR 42mm?
If so why does RW send it with a 142.5?

2: Same question on the Pilot jet...

The reason I ask is I am having a hard time with the new 42mm... With the stock carb it ran good and I can judge jet sizes by the original and get them in the HSR style jets.

 

yes, mikuni jets with the large head have the same hole as the ones with the small head if the number is the same. Don't know why they have two different head sizes.

The reason the HSR flat slide carbs use smaller jetting is because the vacuum is greater - they suck as much fuel through the smaller jet as the BSR sucked through the bigger. The BSR has a vacuum operated slide, and vacuum is wasted to operate it. The flat slides utilize all the vacuum for fuel delivery. I ran a Dynojet 200 in my stock carb - translates to about a 190 Mikuni - but use a 150 in my HSR45.

 

So would you say the 142.5 is about right? How much differacne is there in 150-140? is it small enough that you would not notice it unless you have a stop watch??
Does the Pilot Jet alter ANY performance other then Idle?