10 psi pop off difference between mag and pto

[k_dog345]

As the title states. My pto is popping off at about 50psi, while my mag carb is popping off at 40 psi. Is this too much of a difference? I cannot seem to get the psi up on my mag carb, I changed out the needle and seat, tried the old ones as well. Tried the different springs. I also verified there is no damage in the carb that I can see, I was able to clean it up pretty good....help!

Thanks in advance

 

[Pwnage1337]

That's too much. They should be damn close like 1-2 psi.

Can you take pictures of your pop off setup? How are you holding pressure in the carb? The only reason I ask is because one of the carbs has the fuel pump and it is easy to screw up the hoses when testing pop off. I'd double check and make sure you are pressurizing the "inlet"

 

[k_dog345]

The carb is holding pressure just fine. It’s just the pop off psi which is off

 

[k_dog345]

Hmm, well, I used a spring in the carb rebuild kit that was actually a touch longer than the original spring. And I was able to get it to pop off at 50psi..... hoping that’ll be ok! I see advice everywhere here that recommends not using the spring from the rebuild kit. I did get a genuine mikuni rebuild kit

 

[mikidymac]

No, don't use the springs in the kit. Only use the spring that is correct for your ski, period.

 

[k_dog345]

No, don't use the springs in the kit. Only use the spring that is correct for your ski, period.

Any suggestions on how to get my pop off pressure up then? I’m not sure why it would be staying low. As I said, I’ve tried a new needle and seat, tried the old, a combination of the two. I’ve also tried using new and old arm/pin. I couldn’t get it above 40PSI. The only thing that got it up was using the longer spring.

 

[k_dog345]

This is incredibly frustrating. I’ve bent the arm, probably more than I should. I could get it up to 45psi but I notice my needle is leaking bubbles in the wd40. Using different arms gave me no better results. I used the new seat and oring and found that I couldn’t get the pop off above 40 no matter what with the new seat....at a total loss here

 

[Pwnage1337]

What ski do you have? Pop off on my 96 XP was 32 if I remember right.

I did a set of carbs for my friend who had a GTI with the 717 and it was 52

 

[mikidymac]

The only thing that controls the pop-off is the arm, needle/seat and spring, that's it.

Your 1996 SPX uses the black 80 gram springs and 1.2 needles and seats. Do not use any aftermarket parts and don't bend the arms more than 1-2mm. You might need new arms at this point. Seats should never bubble.

 

[k_dog345]

The only thing that controls the pop-off is the arm, needle/seat and spring, that's it.

Your 1996 SPX uses the black 80 gram springs and 1.2 needles and seats. Do not use any aftermarket parts and don't bend the arms more than 1-2mm. You might need new arms at this point. Seats should never bubble.

thanks for the help... I think I was able to get it. The new needle and seats that I had came with an o ring that was way too big. I could not get the seat in the carb without applying more force than I was comfortable with. Had to use the old seat/oring but I used the new needles. Then I continued playing with the arm, and was able to get it to pop off at about 45 psi. PTO was averaging 48psi. Good enough for me. Got the carbs back on yesterday along with fuel system parts and rotary valve cover. She RUNS, today I plan on taking it out on the water. She was running great on the trailer, hopefully will be the same story on the water......

Your carb rebuild thread helped a lot, along with all the advice you’ve gave so far. Thank you!!!