Useful info!
O.K....I just went back through some information on your carbs. I looked again at the low speed setting for the Mikuni 38 and I did read once again that the initial setting is open 1 turn. Not just for your model SPX, but the XP, GSX, and GTX all run the same carb. No matter though, because it's only a 1/4 turn and it's also just a starting point.
Once you get to that point, your going to start your motor. Checking the low speed screw, you'll look for the following. Does the engine idle smoothly? When pressing pulling on the throttle cable, is there quick, initial response? If not, make small adjustments until it smoothes out on you. If the screws are accessible while the engine is running, then try and adjust them that way. Listen to the sound of the engine. Try and adjust the carbs together, the same. But if your adjusting one and you hear the tone of the engine change, stop and adjust the other. Once you think you got it right, it sounds good, then back off on one carb till it sounds a little rough, then tighten back down till it's smooth again. This will put you on the side of error as rich. It's better to be on the side of rich, moreso than on the side of lean........
The high speed screw starts to work on the carbs after being open, I believe it was 1/3. I'm already forgetting my info. But it did say maximum fuel delivery on the high speed screw is at 3 turns off of seat. Then you can go from there. If you start at three turns out, you start the motor and it runs smooth, low speed should be fine. Testing the high speed throttle will probably want to be done in the water. But when you open the throttle up, if it's running rough, stop ( and i may want to check the plugs to see how much fuel is on them) and turn the screw in a quator turn. Then try again till you find the sweet spot. As soon as you turn it in to the point it's running good, don't go any further because you don't want to lean her out at high speeds.....(eeeks, engine damage can occur).
The Mikuni Carbs manual is in the premimum section and is a very informative and interesting read. It doesn't take that long to read it and in your application, it will probably give you a lot more info on the carbs than the actual seadoo shop manual!.......:cheers:
