Pop-off pressure questions

[kilgorekb]

1. Should both MAG and PTO be the same pressure?
2. During test, I don't get a good pop unless I lube the needle first. Is this normal? These are brand new needles and seats.
3. MAG = 27 psi, PTO = 38 psi. Specification is 38 +/-12. Do I need a new spring for the MAG, or can I stretch it, or make some other adjustment that I don't know about?

FYI... My model has the accelerator pump.

 

[kilgorekb]

Well due to lack of patience combined with boredom, I stretched the spring just a hair. This increased the pop-off from 27 to 45. I then trimmed 1/4 circle off each end of the spring with fingernail clippers, and that put it right on the money at 38. I'm sure someone will let me know if this is an incorrect technique.

 

[jdfrye]

just finished rebuiling my carbs and they are sitting on the counter as i type.
heres the guide i used to do it and this does mention what to do and not to do.
and the guide PDF>1,3,2,4 i think.
http://www.seadooforum.com/showthread.php?3495-How-to-Rebuild-your-Carb
When i opened up my carbs the person that last rebuilt them put the "pulse body pump gasket" (super thin black one) on the PTO carb!

 

[Sportster-2001-951C-Stock]

Well due to lack of patience combined with boredom, I stretched the spring just a hair. This increased the pop-off from 27 to 45. I then trimmed 1/4 circle off each end of the spring with fingernail clippers, and that put it right on the money at 38. I'm sure someone will let me know if this is an incorrect technique.

Please try not to modify or damage your original factory springs, they SHOULD work properly as they are.

The mikuni procedure suggests using a lubricant such as WD-40 to assist locating air leaks and the lube helps obtain a consistent pop-off reading, otherwise without lubricant the suggested three consecutive tests may produce various results.

A google search for mikuni super BN SBN carburetor manual should produce a link to the Mikuni PDF manual which contains the entire procedure + much more, you should have this reference material available as you're working.

 

[kilgorekb]

Please try not to modify or damage your original factory springs, they SHOULD work properly as they are.

According to the Mikuni manual, I need the black spring (80g) if the spec is for 38 psi on a 1.5 needle. The ones that were in there were silver with 1.5 needles. Not sure if it was a dull or shiny silver.

The seadoo part number for the spring is 270500313. I have no idea what color that part # spring is.

Also, the Mikuni manual doesn't take into account the models with accel pumps (like mine.) I've read elsewhere that if you have the accel pump, they use 95g dull silver springs instead of the 80g black. Have no idea why the different spring though... pop-off pressure is pop-off pressure regardless I would think. I don't know, I'm just a computer guy.

heres the guide i used to do it and this does mention what to do and not to do.
and the guide PDF>1,3,2,4 i think.
http://www.seadooforum.com/showthread.php?3495-How-to-Rebuild-your-Carb

Yea, that's what I've been using. Really good compilation of Seadoo and Mikuni info.

 

[Dr Honda]

First..... NEVER stretch the springs !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!


Remember... the "Pop-off" test, is just that.... A TEST. It's not how the system actually works when the engine is running. While running, the vacuum of the engine sucks the diaphragm in, and presses on the arm. By stretching it... you change the pre-load, and not the actual motion.


Now to the questions...

1) Yes... they should be very close. Within a couple PSI on the 800's.

2) Yes... you have to put oil on the needle.

3) I shoot for 32 to 35 PSI on the 800. So... order new springs. (65g shiny silver)

 

[Sportster-2001-951C-Stock]

FYI, the 95g silver spring is wound backwards from the other three, that's how you can tell if it's the 95g, the 65g is wound in the same direction as the black 80g and gold 115g springs

 

[kilgorekb]

OK. I'll just get 4 new 65g springs. How can you not listen to a Dr.? They're only $1.79. I gotta wait for the fuel restrictors to come in anyway. Mine didn't have those. #palerider knows what I'm talkin bout.

 

[Dr Honda]

FYI, the 95g silver spring is wound backwards from the other three, that's how you can tell if it's the 95g, the 65g is wound in the same direction as the black 80g and gold 115g springs

You know something.....


In all my years of playing with these things... I've never noticed if they were RH or LH wind. Now, I have to go look.

Kilgorekb: With the pressures above... that's with a 1.5 needle and seat. So... make sure you have the right one.