Only of you have ran the engine out of oil...Sounds like the carbs may not be set correctly.. .Did a professional do the rebuild?..What exactly was "rebuilt".. were any parts replaced?
Sounds like the low speed (pilot jets/air screw passages may not be clean as they need to be??)
Please check the compression on each cylinder..remove the spark plugs... hold the throttle (carbs) wide open when you check this.. spin the motor for 5-8 seconds... you should get 120psi. minimum..(and less than 10psi difference).. if less, it might be time to actually rebuild the top end..(new pistons/rings/hone cyl.).. only bore it if absolutely necessary.. get it measured..
There are only 3 parts in a two-cycle carb that ever need to be replaced,,(unless they are actually broken) The needle and seat assy., the jet needle and the needle jet. ..see pic... parts # 41 = needle and seat assy. #6 = jet needle, #37 = needle jet.
The needle and seat regulate the flow of gas into the carb as the floats rise and fall..,, if they are damaged or leaking the carb will overflow with gas., the needle jet is a orifice with a specific size..The jet needle has a specific size, taper, and length..== The jet needle and needle jet work in unison to regulate the flow of gas from right off idle all the way to WFO..the needle jet/jet needle WILL wear over time causing the fuel/air mixture to become richer and richer and start fouling spark plugs..(this is more pronounced on 4-cycle ATV's)...
I hope this has shed some light on your carb situation...
Good luck...
exploded view of mikuni carb Google Search
SOURCE: 1997 yamaha waverunner 3
My 97 gp760 did this. I checked almost everything. Replace or clean your plugs, then run carb cleaner through your fuel filter both ways, and then spray carb cleaner into the fuel line from the fuel filter to the carbs. Run 10 minutes, more carb cleaner into the fuel line, and run it 15 more minutes. Then zip tie fuel lines at the fuel filter. I figure there was trash or buildup in the carb. Its easier than rebuilding the carb. Try it. Daniel at the MEXPIPE Pto Escondido Oaxaca.
SOURCE: stihl 026 chainsaw is spitting fuel while running
pull your air filter off and try it if it does not spit fuel anymore replace air filter
SOURCE: 1994 Yamaha Waverunner 3 will idle but wont take throttle
Switch to reserve tanke to check to see if there is a clog at the fuel pickup in the tank.
My friend had the same issue with his waverunner 3.
SOURCE: 2004 sportsman 600, bogs down bad at half throttle.
Check that your choke is working correctly
Your timing may be way off as well
SOURCE: Waverunner bogs down on acceleration
Our 1996 waverunner has been running great until this weekend. It seems to bog down after 3 minutes of running at full speed. If you keep it at 3/4 speed no problem, it runs steady. Tried carb cleaner but it still runs the same....What repairs are we looking at. thanks.....
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