Gas not getting to carb

[JoeJoey]

Update on this. Engine was definately bad. We found a donor ski for free that had a working engine. Swapped it out. Worked out some kinks,and we went on the lake successfully last weekend and are going tomorrow. Today we refinished it and removed all the worn stickers. This week we found marine vinyl and recovered the seat for almost nothing. I think we found the cheapest way to get a jet ski on the water

 

[motoring]

There’s no tune on these.
Basically if it’s a stock ski it will run perfectly on the stock settings. If it doesn’t you have something wrong. Carbs should only be rebuilt with genuine mikuni parts.

i see that this post is basically answered . and this answer you gave is where im at. i rebuilt carbs with good kits . pop off is good , new fuel lines etc . eng still runnung like lean i have to pull choke for engine to lower rpm and to sound more normal. the engine at idle is ROUGH SHAKING ROUGH,, no popping or back firing ( . i found a very small bolt rattling around in the flywheel area may not be related )and ENGINE at all rpm settings driving in water always needed choke to be pulled a bit to run pretty good ... where should i go next ?? (96 dual carb gti 717)

 

[mikidymac]

i see that this post is basically answered . and this answer you gave is where im at. i rebuilt carbs with good kits . pop off is good , new fuel lines etc . eng still runnung like lean i have to pull choke for engine to lower rpm and to sound more normal. the engine at idle is ROUGH SHAKING ROUGH,, no popping or back firing ( . i found a very small bolt rattling around in the flywheel area may not be related )and ENGINE at all rpm settings driving in water always needed choke to be pulled a bit to run pretty good ... where should i go next ?? (96 dual carb gti 717)

Pressure test for air leaks. If you keep running it having to pull the choke you are going to destroy it.

 

[motoring]

Pressure test for air leaks. If you keep running it having to pull the choke you are going to destroy it.

i seized it up ,last year, i did compression check its good got lucky ... i just rebiult carbs again.with factory parts, i checked for air in the fuel line side of things . i pressure checked things with a gauge i eliminated the selector dont see any fuel leaks . i dont see any fuel leaking out the crank seals . i do premix its a personal preference. im going to spray something like start fluid carefully with a fan blowing thru compartment etc , to see if the rpm changes to see if air is being drown into the combustion chamber some how . i dont want to take motor apart is there anything other to look into . i havent run ski in water yet after latest rebuild of carbs . but im sure the idle isnt good even at idle the choke is needed. and very rough idle engine bouncing rough the rough dont get better from pulling choke just the quality of idle become more normal... . i used oil pump as a block for the hole instead of buying whatever they sell to block hole i figure why wait for a part to show up i just removed the gear and left the pump and small oil lines as factory , is there anything that will let air in. the cylinder that seized was the flywheel side. i guess ill check pop off again ?? after leak check block . . is there a post on syncing the two carbs ? i believe i have everything covered but im fairly new to the 717 , im missing something usualy something simple.. thanks for help

 

[mikidymac]

You need to cap off the oil ports on the intake manifold as it can suck air through the oil pump if it isn't being fed oil.

 

[motoring]

You need to cap off the oil ports on the intake manifold as it can suck air through the oil pump if it isn't being fed oil.

im out the door that sounds highly probable, should i pull pump and wait for the plug they sell also

 

[motoring]

You need to cap off the oil ports on the intake manifold as it can suck air through the oil pump if it isn't being fed oil.

just checked i left the feed line connected to pump. only removed gear and cable. when i did the job i thought of that unfortunately at this point that would have been a nice fix !

 

[mikidymac]

I would at least cap off the oil line to the pump. It will not cause an air leak but it could still drain oil into the engine if the check valves aren't holding. Also if the little oil lines do break they will let air into the engine.

 

[motoring]

I would at least cap off the oil line to the pump. It will not cause an air leak but it could still drain oil into the engine if the check valves aren't holding. Also if the little oil lines do break they will let air into the engine.

yes good point. cap the lines with what ? for now my rough idle, and lean idle, i would think i can continue on without capping those oil lines.(until i find my problem ) i am getting some oil loss out of the oil tank i figured it was the crank seals and wasnt very worried, after a year and half i got a few onces out the exhaust on start up.. hopefully its all from the oil pump ,at least only some.
the previous owner said he changed the carbs . are the 787 carbs the same. or a smaller engine maybe my jets are wrong size?

 

[mikidymac]

They are not the same even though they are both called Mikuni 38 the 720 uses 38mm butterflies but the 787 uses 40mm butterflies so they would be jetted differently than stock if swapped. Here are the specs per model Seadoo Carb Specs.

 

[motoring]

They are not the same even though they are both called Mikuni 38 the 720 uses 38mm butterflies but the 787 uses 40mm butterflies so they would be jetted differently than stock if swapped. Here are the specs per model Seadoo Carb Specs.

thanks , i did pressure checks didnt find anything wrong seems like the idle is good now ( im thinking the little bolt i found in the flywheel area that was bouncing around and possibly messing with the timing some how . i ran ski with a pressure gauge on the return line didnt get a reading if anything it was less then 1 psi , i dont know if anyone ever record fuel pressure in the fuel system with engine running?? ? like whats should pressure be before the pulse and in and out of the carbs etc etc ...is there a troubleshooting benefit ? i do know the pressure relief is to open at 3 - 3.5 . i pressurised the entire fuel system too 2.5 psi (i didnt hear any air leaks )
it idles better then yesterday , seems like the lean issue is fixed really not sure how..but the motor runs nice with out pulling the choke... engine runs rough still like vibrating it is bouncing around pretty good (i just changed motor mounts three were bad maybe because engine is rough like out of balance would that be normal for a 717 ????????????????

thanks much !!!!!!!!!!!!!!!!!!!!!!!

 

[motoring]

all the help i received greatly appreciated . i should be good to go !

 

[mikidymac]

No reason to check fuel pressure on the carbed skis as it is under vacuum before the fuel pump and open to the tank after the carbs so it isn't going to build fuel pressure like and injected system.

 

[motoring]

i checked you tube and my engine shakes as shown in videos its simpley not a smooth engine. i didnt think it would be, only two pistons with fairly large displacement. im ready to run in open water now thanks much !!!!!!!!! the carb kit was key and getting rid of grey lines if it wasnt for this site i may never have had the ski running good , and i have a good ski trailer for 1k total for both with all parts , i fixed fuel guage . . next issue fix speedo and would like to add a tach need to find where to tap into for signal wire.