More carb questions

[Bartoncraft]

OK...I'm at a loss and so damn frustrated. 97 seadoo challenger with 787 engine. I have rebuilt the mag side carb with all genuine mikuni carb kits...everything. Needle seats, gaskets, o rings, all GENUINE mikuni. I have a second used mag side carb that I cleaned up as well. The first one after rebuild will not hold any air. Like none. DIY pop off tester that worked fine on the PTO side carb. So I took it apart and rebuilt the other used carb I had cleaned up. Again, holds no air to develop pressure. Like pump forever and no build up. Both times using full on genuine mikuni parts with the correct springs and all gaskets orings, needles and seats. I have the pump side hose going in the inlet side and have the outlet side blocked off with another hose that's capped...is something else supposed to be shut off? What am I doing wrong

 

[burtshaver2021]

So when you say it won’t hold pressure, is that with the metering side cover put back on or can you still see the needle and seat?

 

[Bartoncraft]

Holy crap...I found the problem with soapy water...when I bought the mikuni kit it came with instructions that I followed to the letter.....bbbbuuuutttt the instructions included certain gaskets in places...well soapy water showed it leaking air from the pump side. I pulled up the parts diagram on seadoo forum and looked closely. Turns out that I had two gaskets that were not spec for that carb. Once I reconfigured and got it set up per the parts diagram BOOM! pop off and holding air. Now, what is the correct pop off for a 97 seadoo challenger? I think it shares the same engine as the 97 GSX but I am not completely certain. anyone know where I can find that chart? The chart I did find for the 97 gsx has a pop off range of between 23 -43 which sounds like a really wide range. SHould I just aim for the middle of that range? I don't want to run it too lean.

 

[Bartoncraft]

I rebuilt my carbs with genuine mikuni kits. PTO pops at ~ 32 and mag ot ~ 34 or 35. Problem is I had to use two different springs from the Kit to get pop off close. Questions: how close do the two values have to be? And what is the preferred weight spring for 787 from a 97 challenger

 

[Venturian1]

Whatever you found to be the PTO side pop-off pressure, you should get the mag side as close as possible to it.
They need to be as close as possible. Also make sure the throttle plates are in sync by backing off the idle adjustment, and looking from the bottom side, the amount of light you see barely visible around the butterfly should be the same on both sides. If no one has monkeyed with them, they should be the same as set at the factory, kind of like the springs that hold the needle valve closed, and make sure that the needle arms are both level with the floor of the carbs.

 

[Bartoncraft]

I rebuilt my carbs with genuine mikuni kits. PTO pops at ~ 32 and mag ot ~ 34 or 35. Problem is I had to use two different springs from the Kit to get pop off close. Questions: how close do the two values have to be? And what is the preferred weight spring for 787 from a 97 challenger

 

[Venturian1]

I believe its the black 80g spring. They don't have to be exactly the same, within 5 psi is acceptable. Also, since its apart already, remove the pilot jet, and slow speed adjustment screw, then thread it (air/fuel screw) back in one turn and spray carb cleaner or brake parts cleaner into the pilot jet hole, while watching inside the bore of the carb to verify that its coming out in three places inside the bore, two tiny little holes and one a bit larger.

 

[Venturian1]

I've found the 1988-2003 specifications manual to be very helpful. Free pdf download.

 

[mikidymac]

95 gram spring with 1.5 needles and seats. Do not change springs to chase pop-off. Always run the correct springs and needles and seats.
With new arms and pins pop-off should be close.