Mikuni Carb Rebuild Kit

[abby8]

What size rebuild kit do I need for a 99 seadoo gs and does it come with everything I need to do the job, besides the pop-off pressure gauge? I read the carb was 56 mm but I can't find any kits that size, so I think it must be wrong. I am gonna give it a shot, but I might end of taking it to the shop. Where can I get a pop-off pressure gauge (an auto-parts store, or boat ship?)? Thanks for all the help.

[frankey01]

Re: Mikuni Carb Rebuild Kit

they are not 56's you should be able to just go in and buy the kit. or order here from SBT.

[Bill O'Neal2]

Re: Mikuni Carb Rebuild Kit

You need an SBN carb rebuild kit part # 35-160 $35.00

If you had a pop off tester you could verify that the needle and seat is good. Neeles and seats are not sold with rebuild kits.

[abby8]

Re: Mikuni Carb Rebuild Kit

So, if I get a pop-off checker I can see if they are good and if they are then is there a need to rebuild the carbs or not? Also, what kind of numbers am I looking for when I check it? Thanks

[Danny Roszell]

Re: Mikuni Carb Rebuild Kit

Purchase a Pop-Off guage. You will use it for several maintance operations, pressure test fuel system, pressure test jet pump, and performing a leak-down test on your carbs.

You will need replacement gaskets for the fuel pump side of the carbs in order to check the pop-off. So yes, you will still need a carb rebuild kit and carb to manifold gaskets.

[Bill O'Neal2]

Re: Mikuni Carb Rebuild Kit

Danny,
It is not necessary to even remove the fuel pump block to check the pop off pressures or to apply preesure to see if they leak.

Abby,
A rebuild kit comes with all of the gaskets, diaphrams, check valves, filter and rubber parts that is necessary to completely rebuild a carb and a fuel pump that is on the side of the carb.. What is not supplied is the base gasket and the needle and seat.

Once you know the needle and seat size and the oem spring size, you refer to a Mikuni pop off chart to see how much PO pressure you are suspose to have.

These facts and figures are all in the service manuals. Most of them are on the SBT videos here in the technical forums.

[Danny Roszell]

Re: Mikuni Carb Rebuild Kit

Good to know Bill. Some articles talk about testing at the fuel filter orifice to get in front of the check valves.

[Bill O'Neal2]

Re: Mikuni Carb Rebuild Kit

Humm,
I wonder how you could do that, being that the fuel inlet fitting is on the side of the carb and if you remove the fuel pump air won't go into the needle and seat through the filter. Do they mention putting a fuel pump block-off plate on the carb before testing, like the one on one of the two carbs in a set ?

From a Sea Doo manual in the carbureator section:

Pop Off Pressure Test

Install pump guage tester on inlet nipple.
Obstruct outlet nipple with finger.
Pump tester until inlet release pressure is reached ( seen by a sudden drop in pressure).

Refer to following table for specifications of the pop off pressure for each model ( vintage 1996 SD service manual).
SP, SPI, GTS, 21-37 psi , 14 psi minimum stablized pressure.
SPX, GTI, HX 40-56 psi, 24 " " " "
XP, 27-39 psi, 15 " " " "

*Note* Pressure test should be performed three times to obtain a valid reading. If release pressure is not within specification, check control lever arm adjustment. Replace spring as necessary.

And I might add to make sure the needle is not stuck and is wet with gas or WD40. And, I test them with the diaphram and cover off of the carb, with the carb laying so the needle and seat are facing up in a pool of liquid ( gas or WD40). Stand back or get it in the eyes when it pops off.

Nowhere does it say to remove the fuel pump from the carb.

[Danny Roszell]

Re: Mikuni Carb Rebuild Kit

Tech Articles - How to Check Pop-Off.

NOTE: You cannot accurately test with the pump body and fuel filter still attatched to the carb - you MUST disassemble it and test directly into the fuel inlet orifice, where the fuel filter sets. Otherwise you are testing through the pump checkvalves, throwing your readings off, too high. If you have an external fuel pump, this does not apply.

I'll never claim to have the understanding of these carbs that you do, I simply go over printed information until I remember it and try it when required on my stuff. If the information is wrong, I'm wrong.

[george]

Re: Mikuni Carb Rebuild Kit

one wonders why then the mikuni pop off tester comes set up with the fitting to attach to the inlet tube. It is a real pain to get a tube to seal to the internal orifice. (If there is a special fitting of some sort for that I'd like to know.)

[Technical Support]

Re: Mikuni Carb Rebuild Kit

I was taught and always recommend when possible to remove the fuel pump plate and use the tester with it's adaptor right in the carb body to the N&S, as it's designed to do. Using it through the fuel pump check valves has a slight effect on the reading. Either way gets the job done, but if you have the carb apart, do it the best way.

[Bill O'Neal1]

Re: Mikuni Carb Rebuild Kit

I sell lots of genuine Mikuni PO testers. Never seen an "adapter" ???

I also don't have any problems doing it the way it was decribed in the sevice manual. Works for me.

[Technical Support]

Re: Mikuni Carb Rebuild Kit

It's the black cone shaped piece on the end of the line.

See:

[Bill O'Neal1]

Re: Mikuni Carb Rebuild Kit

Lean something new everyday !

I just use that hose on the fitting. 15 years now.......... LOL!