Over reving

[makxc50099]

Hey everyone,

I have a 1996 sea doo XP. The problem I am having with it is the engine when out of the water over revs. It will be idling at the giving RPM in the manual then shoot up to around 7k and not come down. I can pull the key and the plug wires off but it is acting like a diesel and not shutting off. The only way to stop it is by covering the Carbs up with my hands. The jet ski stopped running right 2 years ago and I put new Carbs on it and that is when this problem started. Does anybody have any ideas what could be causing this? Any help would be greatly appreciated.

Thank you,

Matt

 

[makxc50099]

One more thing. I also added a primer system to the Carbs.

 

[Dr Honda]

its running lean. turn the low mix screw out 1/4 turn.

 

[jhjesse]

You are sucking air somewhere. Look around the base of the carbs and make sure the base gaskets are installed correctly. Check the bolts that connect the carbs to the intake and make sure they are tight.
It is possible that one of the base gaskets slipped during installation of the new carbs.

At any rate, you need to find the air leak, hopefully before cranking it up again.

If possible...remove the flame arrestor start it. Then take some WD40 with the little plastic directional tube and lightly spray around the base of the carbs, if you hear a change in the idle, you have found your leak. Good luck

 

[Dennis]

There is also the possibility that the new carbs are not jetted correctly for your 787 engine. If the advice from the other posts does not help then you might pull the carbs and check for proper jetting. You're supposed to have a 142.5 main jet and a 70 low jet. Mixture screw settings: 0 turns out on the high speed screw and 1 1/4 turns out on the low speed screw.

DAWG

 

[scooper77515]

Where did you get those carbs, and what are they off of?

I have never seen a gasket at the base of the carbs on either of my 787s. Do they have one?

My boat did this runaway throttle on me twice, but I riched it up 1/4 turn on low speed mix and it has been fine since.

 

[Rotor13B]

Where did you get those carbs, and what are they off of?

I have never seen a gasket at the base of the carbs on either of my 787s. Do they have one?

My boat did this runaway throttle on me twice, but I riched it up 1/4 turn on low speed mix and it has been fine since.

When I purchased my gtx's One of them had a slight acceleration problem and so I pulled the carbs off of it to clean. Initially I thought It was missing the base gaskets but after a closer look i realized they were there but perfectly shaped like the base the carbs screw to. I was able to peel them as a whole piece. Next time you have them out (carbs) check the base and the bottom of the carbs carefully. Maybe use a razor blade to lift the gasket.

 

[makxc50099]

I pulled the carbsoff last night and the gaskets look good. I cleaned them and will try it again when it stops raining here. I thought that it would of been a rich mixture? What would make a lean mixture do this? Also could the pop off pressure be part of it? I am going to check that tonight

 

[makxc50099]

So I pulledx the carbs off hoping for someting but didn't find anything really. I am gvoing to put them back on tonight and test it when this rain stops. I am wondering why you think it would be lean. I thought it would be to rich. Also, would the pop off pressure have anything to do with it? I am going to check that tonight

 

[makxc50099]

So the post I made this morning didn't show till I did the second one thinking it didn't post so sorry about that. I did check the jets. They were the correct ones.

 

[- BiRkS_]

Its a lean issue, because the less fuel/more air the engine gets, the faster it will run. Pull your plugs and look at the colour, if they are greyish, you are running lean. Turn the mixture screw out a 1/4 of a turn and go from there. In case you are wondering, a rich issue is usually when the engine sputters and chuggs when you hit the throttle. Odds are the engine doesnt want to idle when its rich. Your plugs will also be black/dark and fuel soaked if its running rich.

 

[jhjesse]

Its a lean issue, because the less fuel/more air the engine gets, the faster it will run. Pull your plugs and look at the colour, if they are greyish, you are running lean. Turn the mixture screw out a 1/4 of a turn and go from there. In case you are wondering, a rich issue is usually when the engine sputters and chuggs when you hit the throttle. Odds are the engine doesnt want to idle when its rich. Your plugs will also be black/dark and fuel soaked if its running rich.

Turn the screw in (clockwise) to richen the fuel.
Turn the screw out (counterclockwise) to let more air in, or lean the mixture.

 

[Dr Honda]

Turn the screw in (clockwise) to richen the fuel.
Turn the screw out (counterclockwise) to let more air in, or lean the mixture.

We use normal fuel needles, not an air bleed system, so you have that one backward.

open for more fuel, close for less.

 

[onebadcav00]

Where did you get those carbs, and what are they off of?

I have never seen a gasket at the base of the carbs on either of my 787s. Do they have one?

My boat did this runaway throttle on me twice, but I riched it up 1/4 turn on low speed mix and it has been fine since.

they always have gaskets, i had the same problem last year. it ended up being a bad gasket

 

[makxc50099]

It hasnt run long enough to change the color of the plugs yet. lol. I think before i put the carbs back on I will order new gaskets for it as well. I didnt have time tonight to check the pop off pressure though so that will have to wait until thur. to do now.

 

[jhjesse]

We use normal fuel needles, not an air bleed system, so you have that one backward.

open for more fuel, close for less.

Now what the hell was I thinking!!! Don't get old...if you do make sure you don't get CRS disease. LOL

 

[makxc50099]

hey everyone. I know it has been awhile since i gave an update on things but i finally had a chance to get around to trying it again today. it no runs without running away from me from what i can tell. i just can not get it fine tuned now. it bogs and basically stalls if i give it throttle on the trailer. i decided since it was taking so long just to run it on the trailer in the lake afterwards and it would barely run when there was a full load on the engine. i turned the low speed out to about 1 and 1/4 to 1 and 3/8 and it would at least idle but still wouldn't run. any suggestions?

 

[makxc50099]

any one have any insight?

 

[- BiRkS_]

go to canadian tire/equivilant store and buy a compresion tester. (about 20-30$) with the throttle wide open, crank the engine and get the numbers. If its anywhere below 120-130 psi, you will need a rebuild.

 

[makxc50099]

both cylinders have 150ish psi.