Why is my needle and seat behaving this way?

[k_dog345]

Working on a 1996 Seadoo SPX.

I got two new genuine Mikuni needle and seats that I tried adding in my mag carb. Both have the same behavior of popping off at 60psi, there are bubbles coming from the the seat that leaks down pressure to about 40 psi then it will normally stop. This is on my mag carb. Pto carb does not have this issue. Anything I should be looking closely at? Symptoms on the water are hard startup and hesitation to accelerate until I get past the dead spots then it runs fine. Here’s a video

Could this part be the issue? I cleaned it as well as I could, but the metal tab that holds the mylar valve still had a little bit of rust damage. Wondering if this is the source of the bubbles...

 

[GGuillot]

Have you tried different springs?

 

[Pwnage1337]

How clean is the bore that the seat sits in? I had a problem with one of mine leaking and it was because there was a slight amount of corrosion built up around the bore where the o-ring seats. Once I cleaned that up everything was okay

 

[k_dog345]

Thanks for the tips, I will check the bore and spring.

 

[k_dog345]

Cleaned out the bore, tried new springs. Still noticing bubbling coming from inside the seat....any suggestions?

Only good thing I have going here is pop off is finally consistently at 60psi using genuine mikuni needle and seat. But if I’m not mistaken, the bubbling will give me issues

 

[k_dog345]

Update, I’ve redone some gaskets on fuel side and replaced on mylar film that looked like the rubber stop had a bit of damage.

Now the mag carb is popping off at 60psi, drop 8psi, then it will bubble at the seat until it’s down to about 50psi and it will stop usually. I’m not sure about the bubbling, but maybe I should be happy with the result?

 

[GGuillot]

Cleaned out the bore, tried new springs.

What #springs are you trying? The only thing I can think of to cause such a high pop off would be the spring pressure.

 

[k_dog345]

60psi is the high end of what my Sea-Doo is calling for, which is good. 50-60psi is the recommendation. I don’t think it’s the spring

 

[GGuillot]

60psi is the high end of what my Sea-Doo is calling for, which is good. 50-60psi is the recommendation. I don’t think it’s the spring

Your call, go back out and run it at 60 psi pop off. A different #spring is the only thing that'll lower it...

 

[k_dog345]

Your call, go back out and run it at 60 psi pop off. A different #spring is the only thing that'll lower it...

I appreciate what you're saying man. I don't think PSI needs to be lowered, it's within specification for my 1996 seadoo SPX. And, correct me if I'm wrong, from what I understand it's better to be on the high side for pop off pressure. I'd want to know why being on the high side is bad (if it actually is) before I adjust the arm to lower it

I'm mostly concerned about the bubbling that happens. There's a 'pop', should be a drop of 10 PSI with no bubbling. Instead, I get a 'pop' at 60 PSI. 8 PSI drop, with bubbles from within the seat until it finally drops to a total of 10 PSI and it will _usually_ stop. And the behavior was the same no matter the actual pop off pressure PSI. No telling if it'll bubble to a lower PSI on the water, I couldn't get it to happen on my workbench which I guess is good news *shrugs*

 

[mikidymac]

Your needle and seat are bad for some reason or the arm is letting them open. They should never bubble and bleed off pressure.
1. Make sure they are new and genuine mikuni needles and seats and the correct size.
2. Make sure you are using the correct genuine mikuni springs for your model.
3. Try new arms and pins.

 

[k_dog345]

Your needle and seat are bad for some reason or the arm is letting them open. They should never bubble and bleed off pressure.
1. Make sure they are new and genuine mikuni needles and seats and the correct size.
2. Make sure you are using the correct genuine mikuni springs for your model.
3. Try new arms and pins.

Thanks man, you're always super helpful. I've done all three actually. Tried two new geniune mikuni needle and seats (had an extra sent to me in the mail). They are both the correct size, I'm 100% sure. I even tried knockoff new SBT needle and seat that I had to make sure I'm not crazy (bubbling was actually WORSE with these!). I also am using the correct spring (using original, it's not bad from what I can tell). I've tried a variety of arms/pins (new and used). Still banging my head against the wall! Could there be anything wrong with the carb that I'm just not seeing? Is there a possibility that maybe I've played with the arms too much? I've made adjustments on all arms when testing.

 

[k_dog345]

Another question I'm interested to know if anyone has the answer to. Is there any source out there to just buy a whole new mikinui carb upright? All I could find are used on ebay, and I'd hate to go that route.... I'd be surprised if new mikuni carbs for this year of ski would be available, but hey you never know!

 

[mikidymac]

PM me your address and I'll send you two new levers and pins.

You can buy new carbs from OSD seadoo. And I have on my GTI when nothing else worked.

 

[k_dog345]

@mikidymac is the MAN! My issue was the pin and arm. I must’ve played around with them too much trying to adjust. Thank you so much!

 

[mikidymac]

@mikidymac is the MAN! My issue was the pin and arm. I must’ve played around with them too much trying to adjust. Thank you so much!

AWESOME! So glad you were finally able to get this figured out and glad to help.