Please help!

[Monster12valve]

Hi everybody, I am new here. Just bought a 1997 Seadoo sportster single engine. The boat is in mint condition, except.... it starts great... I idle or low throttle, through the no wake zone on way to open lake (5-7 minutes) runs great. Get to open water get in the throttle, it accelerates, then stalls. Starts back up, and the same thing happens. The motor is fresh, 138psi in each cylinder, carbs were just bought (re builds), I am at a complete loss. It runs great on the trailer, revs to the sky! No issue. Something else weird, when I first went out yesterday... first time, it stalled like above, but when I went to restart it... solenoid just clicked, jumped it... started up. Replaced solenoid (from Seadoo) today... started right up, got on lake, stalled, went to restart, just clicked. Hit the starter button about 5-10 times, then started cranking great again, i then came back straight in. Can anybody help me? It’s almost like the solenoid over heats, but the stalling issue is killing me. Plugs are brand new too, today was first trip with them new.

 

[Monster12valve]

Hi everybody, I am new here. Just bought a 1997 Seadoo sportster single engine. The boat is in mint condition, except.... it starts great... I idle or low throttle, through the no wake zone on way to open lake (5-7 minutes) runs great. Get to open water get in the throttle, it accelerates, then stalls. Starts back up, and the same thing happens. The motor is fresh, 138psi in each cylinder, carbs were just bought (re builds), I am at a complete loss. It runs great on the trailer, revs to the sky! No issue. Something else weird, when I first went out yesterday... first time, it stalled like above, but when I went to restart it... solenoid just clicked, jumped it... started up. Replaced solenoid (from Seadoo) today... started right up, got on lake, stalled, went to restart, just clicked. Hit the starter button about 5-10 times, then started cranking great again, i then came back straight in. Can anybody help me? It’s almost like the solenoid over heats, but the stalling issue is killing me. Plugs are brand new too, today was first trip with them new.

When I say “jumped it” I mean jumped the solenoid, the battery is new.

 

[Dr Honda]

Carbs aren't right. I'm guessing the pop-off is high. Basically... the regulator diaphragm gets sucked in, and lets fuel into the carb... in turn, feeding the engine that creates the vacuum that sucks in the diaphragm.

When the spring pressure is too high... you basically just suck the carb dry, and don't make enough Vac to overcome the spring... and fuel doesn't flow.


So... take the carbs apart, and verify that all the internal parts are OEM (not crappy aftermarket parts) and that they are built to the factory specs.

 

[Monster12valve]

Thank you, I will try that tomorrow. The previous owner had this same problem I believe, and that’s why he got rebuilt carbs for it. But I will def check it out tomorrow

 

[Monster12valve]

Also this is a dual carb setup, the low screws are set at 1 1/4 out, and highs are both closed, does that sound about right?

 

[Dr Honda]

Probably... but let me verify.

The reason we see settings like that is... the low screw is the actual fuel setting for a closed butterfly. (when there isn't enough air going past the venturi in the carb) the high screw is just a fuel adder, to supplement the main jet.


Hu,,,,,,,,,,, ok...... my brain just kicked in. (had enough coffee this morning) Since it's shutting off at higher throttle settings... there is a check valve in the carb. It keeps the low/mid section from sucking the carb dry. If it's leaking... then there isn't any fuel for the transition to higher RPM's. The little screws are a pain to get out sometimes, and guys don't replace them during the rebuild.


As far as OEM... the parts are easy to see. The Mikuni diaphragm has a red nipple in the center, and the needle/seat/jets will have a stamp that looks like a window pane. (4 squares)



*******EDIT******

yes... 1-1/4 low, 0 high.

 

[Monster12valve]

Probably... but let me verify.

The reason we see settings like that is... the low screw is the actual fuel setting for a closed butterfly. (when there isn't enough air going past the venturi in the carb) the high screw is just a fuel adder, to supplement the main jet.


Hu,,,,,,,,,,, ok...... my brain just kicked in. (had enough coffee this morning) Since it's shutting off at higher throttle settings... there is a check valve in the carb. It keeps the low/mid section from sucking the carb dry. If it's leaking... then there isn't any fuel for the transition to higher RPM's. The little screws are a pain to get out sometimes, and guys don't replace them during the rebuild.


As far as OEM... the parts are easy to see. The Mikuni diaphragm has a red nipple in the center, and the needle/seat/jets will have a stamp that looks like a window pane. (4 squares)



*******EDIT******

yes... 1-1/4 low, 0 high.

Great, got the carbs out today after work, will dig into them tomorrow! Thank you very much for your help! I will report back tomorrow with what I find.

 

[Monster12valve]

Ok, pop off pressure is 32psi in both carbs. I found today... that if you pull the choke out a little, it revs great. I checked timing... dead on... I checked for air leaks... found none. Tried unplugging rectifier, no difference. Next I pulled the carbs to look at jets, the pilot is 130 and the main is 62.5, are these to small? Low screws are out 1-1/2 rotations, highs are in all the way.

 

[Monster12valve]

I went ahead and ordered two new oem rebuild kits. Definitely think I have a carb issue

 

[Dr Honda]

I'm not sure if I'm assuming or not... but did you have the carbs off when you checked pop-off? The way you wrote it sounds like you tried while they were still on the engine.

 

[Monster12valve]

I'm not sure if I'm assuming or not... but did you have the carbs off when you checked pop-off? The way you wrote it sounds like you tried while they were still on the engine.

No, we had them off the boat. I think it has to be a fuel problem, because I pull choke slightly and it runs and accelerates great.

 

[Dr Honda]

Yep... if it comes back with the choke... then the carbs aren't fueling. Pop-off is high... aftermarket parts... or the little check valve is leaking.

 

[Monster12valve]

One thing I did notice... not sure if it normal, when running, at idle, the rear carb drips fuel inside, on to the butterfly (the lower one, not the choke. It is a steady drip. Front carb doesn’t do that. I ordered kits to rebuild, oem kits direct from mikuni

 

[Monster12valve]

Ok, rebuilt the carbs today with “Back to OEM” kits. Now it idles very high, even though the throttle blades are back, I checked both new carb to manifold gaskets , and they look good. Any guesses? No fuel leaks, just idles a lot higher than before, even with the throttle adjustment screw backed off.

 

[Monster12valve]

Testing was done out of the water. I haven’t had time to put it in the water yet.

 

[Dr Honda]

If it wasn't in the water... don't try to adjust anything. In water, and out of water idle can be 1500 to 2000 RPM different. Also... most 2-strokes will idle high when cold. (can't get a proper warm up on the trailer)

BUT... if adjusting the idle screw didn't make a diff... then make sure the throttle cable isn't pulled tight. (it may be holding it open a little)

 

[Monster12valve]

Well, since 90% of the threads I searched never said what the fix was... I figure I would post mine. The high idle was due to a bad rear carb low fuel needle O ring. I must have overlooked it (I did the front carb) I changed it out with a new seal, fired right up and runs great.