300/440/550 JS550 jetting
- Thread starter olnick550
- Start date
jetski9010
Team RTYD
- Location
- Lancaster PA
Do you still have the stock round body BN carb on it? If so it doesnt take jets. The only way to tune it is by opening up the high and/or low jet needles? Where in PA are you at?
How could this BN carb not have any jets? It is a not a float style carb nor is it a constant velocity carb. I am pretty sure all Mikuni carbs for watercraft applications have jets, without them they would not function properly.
Nick, this stock carb might not be able to handle the amount of fuel the motor is going to need after you install the exhaust, regardless of the jetting size that you choose, you might be flirting with the idea of going up to the 40+ mm size carbs.
SUPERTUNE
Race Gas Rules
- Location
- Clearwater Fl.
The BN series carbs DO NOT have jets, they do have a fixed main jet that is not removable and will need to be drilled bigger to increase more fuel demands when added to the high speed mixture adjuster screw.
This is so old I'm forgetting most of the mods I did on 550's, but I'm pretty sure the stock jet hole is stamped .8, this means the hole is .8mm in diameter. (.031) I'm pretty sure I always drilled them out to 1.0mm (.040).
P.S. If you screw up and drill too big you can silver solder up the main jet hole and re-drill again...
Hfurll
Henry
- Location
- Breckenridge Colorado
drilling out the main is not nessessary unless he gets into his intake and exhaust ports, at that point switching to an SBN will save hours of tune time.
there is alot of power to be found in the 550 ports!!!!
bump your High screw up a 1/4 turn and go from there.
added is a doc of your internals
there is alot of power to be found in the 550 ports!!!!
bump your High screw up a 1/4 turn and go from there.
added is a doc of your internals