Carb rebuild questions

[seadooer2022]

Did couple carb jobs on small outboards before but this is the first time rebuilding a jetski carb.
1. Is it a good idea to submerge the carb in boiling water (mixed with pine sol) then brush the parts
2. Tried to do a quick pop off test, connected the fuel inlet to a hand pump and blocked off the outlet but it's not building pressure, any tricks to this?
Here's what my carbs look like

 

[Ed Clark]

Some reasons why it may not be building pressure:
1. The diaphragm is leaking. Good practice to do a diaphragm vacuum/pressure check early in the going.
2. The pop-off valve aka needle and seat are leaking. Good chance of this on older, cruddier carbs.
3. I have found that using a finger as a block off simply doesn't work well for either vacuum or pressure testing. I'm guessing the fingerprint ridges simply don't allow a good seal, at least in my case. So, I have found I have to use rubber tubing or plugs or some very positive method to block off any ports that I don't want to leak. Don't know that you're using a finger, but if you are ....

 

[RG123]

Just follow the carb rebuild thread sticky exactly, no shortcuts! Keep it simple.

 

[seadooer2022]

Just follow the carb rebuild thread sticky exactly, no shortcuts! Keep it simple.

Not taking any shortcuts, following the thread and watching couple yt videos as I go along，thread says use brake cleaner but in the past I've soaked carb parts in hot water and pine sol with good results the hit it with carb cleaner since I don't have an ultrasoundic cleaner. But pine sol is bad for rubber so I thought I'd asked here first.

 

[burtshaver2021]

I’ve seen numerous posts of people using a pine sol formula, the rubber components are completely removed before hitting the ultrasonic, as they will be if you follow the carb rebuild thread

 

[mikidymac]

Never used any water and pinesol in 35 years working on these but it is your carb so do what you want.
The carb rebuild thread has all the info but we will answer all your questions.

Finger doesn't typically work for checking pressure.

 

[seadooer2022]

This needle still good or no?

 

[burtshaver2021]

It’s a little dirty but doesn’t look grooved . Does it leak?

 

[seadooer2022]

It’s a little dirty but doesn’t look grooved . Does it leak?

It’s a little dirty but doesn’t look grooved . Does it leak?

Just tested, no leaks, holds 10 psi for over a min. results from 3 pop off tests: 22, 22, 20. I guess needle is good.

Other question
Are the hi, low speed adjusters and springs supposed to be painted. read somewhere that the springs were not painted originally? When I wire brushed them, the paint came off, should i bother to repaint them?
Before and after

 

[mikidymac]

Yes, they were painted, they are 30 years old and paint flakes off.

Always replace the needles and seats.

Do a full rebuild with new Genuine Mikuni parts and be done with it. There is nothing to gain from cutting corners.

 

[seadooer2022]

what is the difference between mikuni bn38 and super bn38.
bought two packs of these, the front says it's for bn38 but the back says for super bn38, will these work for a 95 gtx? is mine a bn38 or super bn38?


will this kit fit? comes with needles, OSD Back To OEM Sea Doo Dual Carb Rebuild Kit (1994 XP 657X) [OSD1282] - $134.99 : SEA DOO Yamaha Kawasaki Polaris Parts - OSD Marine, Your ONE SOURCE for DISCOUNT Parts!.
says it's for 94 xp with a 657x which is the same as my gtx.

 

[mikidymac]

The correct carb kit MK-BN38/44-SPR.
Do not use the springs in the kit, reuse your old ones.

If you only need the needles and seats then you don't need to buy the entire OSD kit.

1995 GTX is a 657X engine and uses a 65 gram pop-off spring, 1.5 Needle and Seat.

 

[seadooer2022]

Is this the correct orientation for the needle (L hook is facing the arm)?

 

[seadooer2022]

my PTO carb pop off was 22 (within spec) but if I were to up it a little to say 25, do I bend the arm up (the on the spring)?

 

[burtshaver2021]

No, don’t bend the arm. 3 pounds isn’t going to make a difference

 

[seadooer2022]

So mag side pops at 22 , PTO at 20. But once they pop, they don't hold steady pressure, they keep going down to about 8 then hold, will that be a problem?

 

[mikidymac]

Are you testing with the seat wet with WD40?

 

[seadooer2022]

Are you testing with the seat wet with WD40?

Yes, pushed down on the spring a little then add wd40 each time.
They do hold pressure at 10 psi for at least a minute no problem though, ie: pump it up to 10 psi and hold for a min.

another question, how does the pop off actually work in runtime? for example, if i give it throttle and going at 3k to 4k rpm for 10 min, is the needle constantly pop on/off ? since the crankcase is constantly creating negative pressure, I'd imagine the needle would be hold open all this time, right? so holding stead after pop off is not really necessary, right?

 

[mikidymac]

Pop-off is just a test, has nothing to do with how it actually runs.

They should pop clean and reseal. They should not pop then bleed off pressure.

 

[seadooer2022]

when i put the carbs back on the intake, do i need to torque the mounting bolts? if yes,what is the torque?

nvm. 15 ft/lb, found it in shop manual.
and for my own reference: pop off were 23 - 24 psi for both carbs.

 

[Grim]

One tip, make sure the gasket(s) between carb and intake are on their correct, they have a tendency to slip and it they are not on right it will leak air and cause running issues, double and triple verify gasket placement prior to full torque.

 

[seadooer2022]

putting everything back together tomorrow (throttle cable, choke, fuel lines etc), I'm replacing the oil filter along the way. I dont have a way to prime the oil line since I wasnt able to detach the oil pump from the intake. So i'm planning to do premix with gal of fuel, once the oil injection started going, then add more fuel, does that sound like a good plan?

Also, right now the throttle has no slack, soon as I squeeze the trigger, throttle opens up. So to give it slack, do I loosen these two nuts and pull the cable out slightly?

 

[seadooer2022]

Buttoned things up and put some premixed in the plug holes, it fired right up. Idles is too high thoy, around 4k , I think manual says 3k out of water.

Do I adjust the idle screw or the L screw?

 

[burtshaver2021]

Buttoned things up and put some premixed in the plug holes, it fired right up. Idles is too high thoy, around 4k , I think manual says 3k out of water.

Do I adjust the idle screw or the L screw?

You adjust the idle screw to adjust the idle. Low speed screw is for your first 1/4 throttle or so

 

[seadooer2022]

If I want to do a fuel system leak test, is this how to do it ?
Unplug fuel hose from fuel tank
Connect it to a vacuum gauge and proceed
What psi should I pump it to?
I mainly want to check the intake cover and all the hoses to and from the carbs because those were what I worked on.