Where is 35mm on a carb measured?
Posted: 11:25 am Nov 20 2004
When a manufacturer says the carb is a certain measurement, take a 35mm PWK in this case, where are they measuring that? Is that the throttle valve bore???
It's the bore size of the downstream throat. That part that faces the reeds.
In the PWK, that diameter 'carries thru' to where the throttle valve intersects the carb bore. I don't know that all carbs are the same in that way.
In the 200 'H' model oem PWK, the 35mm runs all the way past the jet block into the intake throat until the increasing bore size of the intake bell (looking at it from the reed side) passes 36mm. **edit*** I misspoke..I have a 36mm carb is where that number comes from...on the oem 200 PWK it would be 35mm. **edit***
In an air striker an overbore can't go all the way thru due to the vanes (the air striker parts) that are placed in the intake bell.
Note that an overbore is not centered on the existing bore. That would screw up the jet block height. An overbore is positioned such that metal is removed from the top of the bore, the jetblock positioning then remains the same.