Build Your Own Pop-off Tester

[Hydrotoys]

Unfortunately BD,
It's the one thing my server company lacks is the ability to give out guest FTP, so if you got something to upload just send it to me and I'll upload it and host it for you.

[beerdart]

Unfortunately BD,
It's the one thing my server company lacks is the ability to give out guest FTP, so if you got something to upload just send it to me and I'll upload it and host it for you.

K Also link from the tuners page goes to bluewater?

[Hydrotoys]

Thx.
Fixed.

[dirkdiggler]

Nice thread

[TX21]

Is there a write up on how to do the pop off testing? I think I read one a long time ago but cant find it. Doing my t-handles right now and cant seem to remeber how to do the pop off test. Billy had some info posted but all I don't know what end to put the tester on.

[TX21]

Does this look right? I seem to be getting 90 psi pop off and I am not sure what I am doing. Am I looking for the needle to pop?

[CDW78]

When I down loaded this, I get an EXE file, and it doesnt work any ways, but Im not not sure why I would get that for some instructions, can some one please advise ?

THANKS!

[akjose]

When I down loaded this, I get an EXE file, and it doesnt work any ways, but Im not not sure why I would get that for some instructions, can some one please advise ?

THANKS!

I've never been able to get it to work either. Must be us old schoolers being behind the times.

I get a .dll missing error when I try to run it...with vista and win7.

I've always wondered why no one has posted the instructions without that file.

[CDW78]

Same OS here.
Since this doesnt work, any one know where I can get the info I am looking for ?

Also,
Can I get a quick shot of what a pop off does and why I need it ?
I will be rebuilding the carbs in 2 gp 1200's soon so looking for some info to help me tackle it!

THANKS!

[akjose]

from Jetskimechanic.com:

"The "pop off" is the pressure that the needle is held into the seat... There is a brass seat with a certain size hole in it. The needle usually made of a viton tip sits in the seat and holds the fuel back from entering the metering side of the carb. There is a arm that holds the needle down in the seat until the diaphragm in the carb gets pulled towards the other side of the arm and causing the arm to raise and allowing the needle to open. The seat is where the fuel comes into the carb fuel reservoir. On these types of carbs the intake manifold pressure sucks the diaphragm in on the carb and that is what pushes the arm that allows the needle to let the fuel in... As you change flame arrestors and make other changes to the motor the amount of pressure needed to open the needle changes thus the pop-off change... To change the "pop-off" you can change the spring that pushes the arm up to hold the needle down. Mikuni makes 4 different springs and they go by colors. You have platium (115 gram), dull silver (95 gram), black (80 gram), and shiny silver (65 gram). Each spring has it's pressure amount that it will apply to the arm. Now in order to get the "pop off" number the brass seat plays a roll also. The size of the hole plus the size of the spring will make the p.s.i. that need to obtain. Mikuni has 5 different sizes of seats. They are 1.5, 1.8, 2.0, 2.3, and 2.5. An example of how it works is take a 1.5 N&S with a 115 gram spring and the "pop off" should be 55 p.s.i. Change the spring to a 65 gram spring and it changes to 32 p.s.i. Now there is another way to change the "pop off" a little without changing the spring or the seat and that is by lowering or raising the control arm. I like to leave it level to the base of the carb but you can move it up or down a .040-.060. You will need a good "pop off" tester to do this right. You can check the website for one. The big question I get all the time is what should my "pop off" be??? Well I'm not here to give you the magic number, because once again each craft is different depending on the modifications down to it. Here is a chart to show the changes:

N&S / Spring 115 gram 95 gram 80 gram 65 gram
1.5 N&S 55 p.s.i. 43 p.s.i. 38 p.s.i. 32 p.s.i.
2.0 N&S 32 p.s.i. 25 p.s.i. 21 p.s.i. 18 p.s.i.
2.3 N&S 22 p.s.i. 20 p.s.i. 17 p.s.i. 15 p.s.i.
2.5 N&S 19 p.s.i. 17 p.s.i. 14 p.s.i. 12 p.s.i.
"

[Tommy Pantsdown]

It seems like a lot of you had issues downloading this, including myself.

It is an EXE file, which I don't like downloading. It seems like this program was something someone probably sold on ebay or something similar. Regardless, I went through and started to PDF it by taking screen shots into photoshop.

It was very helpful for me, so I figured I'd repay karma by taking time to do this.


This is JUST the section on how to test your carbs. I'll try to do the rest of it soon. It's a large file (for a forum database to handle, hopefully it uploads)

EDIT- Won't upload. It's 8mb. I'll throw it up on my site and post the link in a few.

[Tommy Pantsdown]

Here's the first part.

http://www.tommypantsdown.com/GP1200r/MikuniBNPopOff_pt1.pdf

[akjose]

If it asks for a password, let me know. It should be set up to just view.

It needs a username/password

[Predator-x]

Why not use a tyre pump with pressure gauge.
Can??t be more simple.

[lynnboy021]

i know this thread is really old but the link dont work so can someone please give me a copy... thanks