- Location
- California
I have 93 superjet with a 760 and a factory bpipe in it! There plugs have about 2 hours of run time on it, do you guys think it’s running lean?? Thank you
Lean spark plugs?
- Thread starter chadward67
- Start date
Plug readings don't tell you that much. For an ideal plug reading you need to be going wide open, then shut the ski off and swim it in. But they still don't give you the full picture. They're good for seeing if both cylinders are even though. Piston wash is a better indicator of how it's running.
- Location
- California
The top of the pistons look brand new! Like bare metal, and they have probably 20 hours on them
What number is on the plug? If they are NGK #6 then it would be very rich in order to make them that dark. If #9 it would be lean in order to make them that clean. My experience says use #8 and power tune the top screws, then adjust the pilot for good response. Generally it needs to be fourcycling a little at 1/4 throttle. This setting will get you max power and response and the plugs will end up brown. Clean pistons mean they are not getting hot. It takes some long full throttle runs with top screws set near peak rpm before they will turn black. If the pilot is set rich and you seldom reach full power the piston will be clean and plugs dark. The fuel and premix oil you use play a part here so there can be some variation.
- Location
- California
They are #8s. That’s really good info thank you! What should my jetting be? It’s a 760 with a bpipe and after market air filters
That varies from ski to ski and what carbs you have.
- Location
- Sweden
If it that SN with 760 and maybe 38s? Id start with 2.0ns 115g, 75p 135m, low 1turn, high 1-1/14 turn, just my 5cents, whats in it now?
- Location
- California
It has duel 44s on it
- Location
- California
I have 140 on the main and 120 on the pilot
waxhead
wannabe backflipper
- Location
- gold coast
Its not lean then
- Location
- California
So what should the jetting be? If I need to lean it out?
You need to close the top screws and watch peak RPM. If RPM is still rising when the screws bottom ,install a smaller main jet, open the screws and repeat until max RPM is found. I have a 62t 701 with a stock 760 intake. It has 140 mains with the screws open around 1/2 turn out. I would expect your 760 would pull harder and need smaller mains but you won't really know without finding peak rpm first. If you dont have a tachometer then tune for strongest acceleration. Size the pilots by finding best response from 1/4 throttle.
- Location
- Charlotte, NC
depending on your impeller pitch and pump load, your jetting is pretty close. you could probably go to a 130 or 135 main. nothing wrong with being a little rich, your engine will last much longer. if the engine runs good, has no hesitations or hiccups anywhere then id let it rip. to tune you main jetting you really want a tach to tune for peak rpm. to see if youre rich, close the high speed screw and go run it and see if you pick up any rpm. if so, you can go down to a 135, start at 1 turn out and repeat until the rpm drops off then go back up on the screw 1/4 turn.