Do not buy your carb parts from thejetskistore they sell SBT carb kits that will give you nothing but problems if you go by the ski model selector. They do have Mikuni but are more expensive than other places.
Only buy genuine mikuni parts. You can buy the Mikuni MK-BN38/44 SPR kits on Amazon and eBay and needle and seats or order the complete kits from OSD Seadoo.
The nice thing about OSD is you get all the parts and carb base Gaskets in one place.
Sorry about that was never a good photographer. I have not rebuilt them yet was doing like a before and after. There’s two inlets I used smaller one for test. The bubbling was around the seat and was holding no pressure.
You're using a penetrate like W40 on the seat? Rebuild them and try new genuine needles/seats and see if it pops. If you use new oem kits, needles/seats/arms and blk 80 gram springs you should see 34-35 psi on the pop off.
OSD marine or bayareapowersports should have the genuine kits. I think I spent $136 shipped with bayarea which included the 1.5 needle/seats then another $10 for 2 blk 80 gram springs. If you strip the screws taking it apart there's a guy on ebay selling a ss allen head kit for about $9 per carb.
Use everything in kits but the springs, don't overlook the HS and LS needle o rings. And clean, clean, clean, use compressed air and blow it out.
On the fuel pump cover side you will see an arrow in and an arrow out. Your pop-off tester goes on the one with the arrow facing in, you cap off the one with the arrow going out.
That last one looks petty nasty inside for being rebuilt a year ago. Also with all that corrosion on the diaphragm groove you might have a hard time getting it to seal. Make sure you pressure test the carbs once they are back together.
The dual kits I posted above for $136 shipped includes the base gaskets, needles/seats and unopened genuine kits. Only the springs are separate. With OSD, you still need to buy the needle arms separate, since the kits are pieced together from bulk parts and some stuff is left out. My experience doing a carb rebuild for a ski buddy the old/new arms made a difference. My carb rebuilds were dead on 34-35 psi with the pop off using a new arm, spring, and needle/seats.