Carburetor Adjustment, bogs when opening throttle.

[themk]

I want to make sure I've identified the problem correctly, so I can fix it. I rebuilt my carbs with OEM Mikuni parts, however I did _not_ replace the needle springs, since I was told the ones that come in the kits are often wrong. The fuel lines were replaced once upon a time by a BRP dealer, however, they were replaced with new tempo fuel lines, so I'm going to have to redo that again at some point. My PWC is a 98 GSX-L with the 947 motor.

The ski seems to idle fine in water, but idles high on the trailer. The real problem, however, is that the ski will bog down and die when trying to go to full throttle. If I blip the choke, then I can get past the bog and the ski seems to run fine at WOT. I do not hold onto the choke afterwards. The ski can then return to idle, and seems to idle fine again. If I want to get back up to WOT though I have to blip the choke again. The ski seems to only run right at WOT or idle, with no in-between. Clearly, based on the fact that blipping the choke fixes it means that it's running too lean. My question is what adjustments do I need to make. Based on what I've read, it seems like this could be a case of bad pop-off pressure, which means I will probably need a new needle spring. My other question is, will adjusting the high speed adjuster screw make a difference, by setting it richer? I have my high and low speed screws set to the service manual specifications.

Thank you.

 

[etemplet]

It's likely your accelerator pump system causing you trouble. You may have a plugged nozzle, or "both."

 

[1of500]

Not at some point you need to do it now tempo line is not compatible with ethanol pull the carbs verify that the accelerator pump works and the 3 tiny holes in the carb are clear

 

[1of500]

You don't need to buy new carb kits but you should perform a leak down test

 

[themk]

Sorry guys, I got busy and neglected this.

I can hear what sounds like squirting from the accelerator pump when I open and close the throttle without the engine running. Does that mean the pump is working, or is further testing necessary?

I guess I can do a leak down test, I would have to get the tool to do that. I was hoping to not pull the carbs until the end of the season, with only a few more weeks left anyway.

 

[Rabid]

Sorry guys, I got busy and neglected this.

I can hear what sounds like squirting from the accelerator pump when I open and close the throttle without the engine running. Does that mean the pump is working, or is further testing necessary?

I guess I can do a leak down test, I would have to get the tool to do that. I was hoping to not pull the carbs until the end of the season, with only a few more weeks left anyway.

I had the same issue on my 99, the nozzles had some build up in them. It took a lot of carb cleaner to get the goo out using compressed air.

 

[themk]

Thanks, that would make sense. This is starting to sound like a next season project.

 

[POPPS]

The high idle on the trailor indicates fuel starvation creating a dangerous runaway situation,,,you did not mention replacing the selector,,,that would be my first move,,,go through the carbs again,,,make sure the mocro filters are clean and that your 3 bypass holes are clear,,.if you did not change out the springs,,,your popoff should be the same,,,or at worse,,,less,,,since the spring would lose some of its noncompressibility..,you can check popoff,
,,for years,,,i rigged up a bicycle pump to do that,,,these days i replace the springs with the original and seats as well,,,if they are by spec,,,the popoff should be perfect,,,i do the popofff,,,not for that,,,but to see if the seat or carb is leaking.

 

[themk]

Thanks guys. Sounds like my whole fuel system needs a makeover. I also found a leak in the carb base gasket too, so that certainly wasn't doing me any favors. Hopefully I haven't done any damage to the motor yet. Either way, it's probably about time for a new motor anyway, as the crank has 200 hours on it, and we all know about longevity with the 947 engine.

 

[themk]

Oh also, does anyone know where I can get an OEM (made by BRP) fuel selector valve? Also, where can I get the fuel pump accelerator rebuild parts.

 

[L. Dean Ficarro]

Oh also, does anyone know where I can get an OEM (made by BRP) fuel selector valve? Also, where can I get the fuel pump accelerator rebuild parts.

The accelerator pump baffle is on the same assembly order sheet as everything else, shouldnt be hard getting it anywhere. Check the site link to their seadoo parts house and get yo 10% off for being a forum participant.

While you are in there, make sure that the small umbrella baffle (its red) is intact and not full of tempo gunk. CAREFUL: itll break off if you are too forceful! There are built in check valves that build ~3 psi (i believe) before allowing fuel into the venturi. Dont stick anything down there, that’ll be bad too. Just cleaners and compressed air to get the goo out.

I have a 99 GSXL that i had the same issue with, that being a dead spot between 2700 and 3000rpm, which i had to feather the throttle over the hump. In the end i went up on my high jet and needle, set the tune back and ran WOT up and down Havasu all summer long. Keep an eye in the heat, exhaust and idles, tune it while its off and be patient.

TO TEST THE ACCEL PUMP
reach in and manually operate the lever that sits on the throttle wheel, as you slowly advance the position there will be a distinct hiss. Put your finger in the carb opening and make sure each one is operational.
Cheers

 

[POPPS]

That impossible accelerator pump umbrella check valve is holley carb part number 2641..i could not find the mikuni number anywhere on this planet.

 

[L. Dean Ficarro]

That is where i found the replacement i used, its far too big so i had to trim ot back to use it. Kinda ruined three of them but it worked, id have shared that but sometimes i opt against referrals like that.