'00RX jet size?
- Thread starter randy
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Jetting?
Your question is valid, but I'm not too sure I can answer it. The RX 947 naturally aspirated engine is equipped with the Mikuni BN-46i (with accelerator pump) carbs. The main jet on both the MAG and PTO is sized at 162.5 and the pilot jet a size 75. Your low speed screw should be set at 1 and 1/2 turns +/- 1/4 turn. Here's where I go common sense.
Living at sea level on the Gulf coast, I know that the supply of oxygen in the air is what everything is based on for jetting or the fuel/air ratio for combustion. The higher in altitude you go, the less oxygen you have to burn that fuel. By you opening your low speed screws, you've enrichened your fuel/air ratio to much. That's science. You probably should be closing down on the fuel, not increasing it. If your still running the standard size main jet, the 162.5, then my thoughts here is that you should try a jet a bit smaller in fuel delivery. The altitude is going to weaken the performance a bit from one running at sea level, you can't do anything about that. But you can make the engine purr like a kitten if adjusted out right.
Some of the response I'm giving credit to is gained from watching the drag races from the mile high drag track, which I'm sure your familar with, and jetting/available oxygen is always one of the subjects they bring up......every year....
I hope this has shined a little light on the subject for you......:cheers:
Your question is valid, but I'm not too sure I can answer it. The RX 947 naturally aspirated engine is equipped with the Mikuni BN-46i (with accelerator pump) carbs. The main jet on both the MAG and PTO is sized at 162.5 and the pilot jet a size 75. Your low speed screw should be set at 1 and 1/2 turns +/- 1/4 turn. Here's where I go common sense.
Living at sea level on the Gulf coast, I know that the supply of oxygen in the air is what everything is based on for jetting or the fuel/air ratio for combustion. The higher in altitude you go, the less oxygen you have to burn that fuel. By you opening your low speed screws, you've enrichened your fuel/air ratio to much. That's science. You probably should be closing down on the fuel, not increasing it. If your still running the standard size main jet, the 162.5, then my thoughts here is that you should try a jet a bit smaller in fuel delivery. The altitude is going to weaken the performance a bit from one running at sea level, you can't do anything about that. But you can make the engine purr like a kitten if adjusted out right.
Some of the response I'm giving credit to is gained from watching the drag races from the mile high drag track, which I'm sure your familar with, and jetting/available oxygen is always one of the subjects they bring up......every year....
I hope this has shined a little light on the subject for you......:cheers:
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Hey Randy, welcome to the fourm.....With any adjustments always check the plugs to see how it is running. if they are black and carboned up than it is to rich... If the plugs are white than they are too lean... The color of the plugs should be a nice even tan light brown color. The best way to check your plugs is install an new set properly gapped, Than to get a plug reading run it at high speed, be sure you have enough room to reach top speed safely! Next shut it down, do not return to idle. Without getting burned on the hot plugs check them and adjust accordingly. Check it again until you have no hesitiations or bogs from idle to top speed, and the plugs are the correct color. When adjusting the carbs, turn the adjustment screws 1/4 turn at a time and re-test for color and performance. For more info on the carbs, their adjustments, and how they work, you could become a Premium member and down load the Mikiuni Carb Manual. Click on the Seadoo Manual Section at the top of this fourm for more detail and a look at all the manuals availiable for your seadoo.
Karl
Karl
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