I learned so much in 10 minutes that my brain can't absorb it all. Need to go back and watch several more times to truly understand, appreciate and apply this knowledge. Also, love the graphs, cut scenes to hear what the issue sounds like and nice calm presentation. Well done.
I owned a few Yamaha's (superjets)and kawasakis (x2) but I picked up a SPX a few weeks ago for my daughter. Id like to think I know my way around the 2 strokes but the seadoo was having a super tiny slight midrange hesitation. Very little. The plugs are a little too lean for my liking... Found your video as I was trying to see what pop-off and screw settings others were having good luck with. Great video!
I got a 96 seadoo xp and I just rebuilt the carbs with mikuni parts. I have the high speed screw all the way closed and the low speed at 1 turn out. the pop-off measured at 43 psi and 38 psi. It idles good but from idle to 1/2 throttle I can feel it stumble, Once I get past 1/2 throttle it takes off like a bat out of hell. I adjusted the low speed circuit 1/4 turn more out and it didn't seem to make a difference. Should I get softer springs to bring down my pop-off pressure?
Pop off pressure of each carb need to be within 1-2 psi of each other. Don’t forget to turn your high speed screw 1/2 out on the PTO (rear) carb as that cylinder will run hotter. Please watch my recent video about pop off pressure analysis.
So far I have found 3 separate examples from your utube videos. 1st was my missing plastic metering collar in a cdk2 witch I have located. After watching this one I wonder if it was removed to deliver more fuel instead of changing the low speed screw or the pop of limit?
So I have a seadoo GTS 95 model, single carbI've rebuilt carb with mikuni parts from seadoo dealer. With the original spring pop off was 20 psi, with new spring it's at 12 psi I'm confused they both seem low according to the chart, what would be the next step to get the sputter at low speed to go away
If you are changing altitude… going from higher altitude to lower altitude. Seadoo likes to put the highest possible main jet for sea level… and make it 0 turns. If you go from sea level to say 5000 feet, you would need to go a couple sizes lower in the main jet.
So in tuning out a hesitation or fall, we could lower pop off or turn out the low speed adjuster... (and use a larger pilot jet as well I assume) But is there any reason to go one way vs the other? Like it's not very feasible to change your popoff while out on the lake, adjusting the low speed needle makes more sense in the field. But for initial setup on a bench, and I know I have a major Fall condition going on, why should I opt to lower popoff vs adjusting the low speed screw/pilot jet? Are there other "side effects" to take into account? Also, is it fair to say that the low and high speed needles are a form of "finer adjustment" for the pilot and main jets respectively? to give an analogy, like those old school balance beam type scales when you go to a doctors office, where the "big" sliding weight (50, 100, 150lbs) are like the jets, and the "small" sliding weights (1lb increments) are turns on the needles Hope that made sense!
@@neppy5 to answer your second paragraph… yes it’s sort of a finer adjustment. But for Mikuni, once you go beyond two turns out, you need to go up a jet size. This is how you should tune a hesitation in order of feasibility and what Mikuni wants you to do. Remember hesitation on take off is due to a lean idle mixture… so… 1) adjust idle screw to slightly richer the mix… its okay to be just below or above your recommended idle speed as long as it is a smooth idle and takeoff. 2) low adjuster screw… for dual carbs, adjust both at the same time and rate. 1/8 at a time. Give the ski more warm up time and a few take offs before judging If it works. 3) change pilot jet - this will require removing carbs 4) I wouldn’t change pop off unless you aren’t getting anywhere. For most (for example)it’s a matter of going from a 95g spring to an 80g spring. Also, make sure your carbs are probably linked. This causes a rough idle and could affect take off. Make sure you have new spark plugs that are properly gapped, and you have sufficient spark.
@@2-smoke Thank you Thank you Thank you!! I feel like I have a solid plan of attack now. I think my idle currently sounds smooth around 1300, and I actually went like 4x turns out on the low screw, so I'll definitely try a larger pilot jet next
@@2-smoke hey, it’s a 2003 Yamaha XLT 800, 170hrs, pretty much everything stock except the impeller which i changed to a Solas because the one it came with was locked up, wear ring and most cables changed too, around 135 psi compression is both cylinders, dual mikuni carbs, rebuilt with OEM kits, followed stock settings: 120 for the main jet, 90 for the pilot, stock turn outs in needles, 1/2 for high, 1.75 for low, stock silver spring with 1.2 needle/seat yielding around 82psi pop off which is stock, put in new accelerator pump just to rule that out, 1100-1300 rpm idle in the water the ski gives trouble starting, i would have to pump the accelerator many times and crank a few times before it starts, in the water i couldn’t go above 3k rpm and 15mph, the ski would simply not respond to pulling the throttle more, and if i went WOT the engine would stall, also i had to keep pumping the throttle otherwise lightly otherwise it would stall (while moving) Thanks to your videos i’m able to see i had a severe lean condition going on leading to Falls, this week i’ve swapped to a 1.5 needle/seat, now popoff is 55psi, changed the fuel filter as well for the heck of it i am hoping to try it in the water again this weekend, if it hesitates i plan to double check the idle and up the pilot jet to lets say a 95 next apologies if this was lengthy, but i figured the more details the better when diagnosing
@@2-smoke random question if you don’t mind, i changed the needle in seat in one carb, popoff test was successful at 55psi 3 times, changed the other carb and noticed that gas ended up coming out of the fuel in port where the pop off tester was connected, i was super confused and eventually realized that nothing was coming out of the fuel out port, like i applied pressure at fuel in with nothing blocking fuel out, and yet no air was coming out from fuel out my guess is i might have installed one of the check valve’s backwards on the pump side when rebuilding, does that make sense to you?
So with a fall I would start by adjusting the low speed out to be more rich? And if the adjustment is too far put bigger pilot jets in? My 95' GTX carbs are all clean with new Mikuni parts and pop off at 21psi. Idle and first 1/4 throttle is great but anything beyond 1/4 stalls it out no matter how fast or slow I open the throttle. This video is a great starting guide to marine carb voodoo!
Correct. Usually this happens when the idle screw is not where it needs to be. Remember, if you increase idle, you are allowing more air in. Seadoo manuals say the idle screw should be turned in two turns from contact of the lever on the butterfly. Set the low adjusters then, and usually this will be on par with a good take off. Make any further adjustments on water. If you are still having issues, set the idle while running the ski dipped in water (while on the trailer). Make sure ski is warmed up and the idle will be between 1400-1600 rpms. Then turn out your Low adjusters (together) until you hear the rpms drop. When you hear them drop, turn them in slightly. This is how to correctly set idle. Side note, idle rpms out of water is 3k.
