High RPM'S And Wont Shut Off !!!!!

[97SeadooGSX]

I had the 96 XP out for an hour+ with no problems today running hard. I did run it out of fuel so I put it onto the reserve and headed in. Got out of the water ok. Got home and went to flush the ski, after 30 seconds of flushing it started running high rpms outta nowhere. I pull the DESS kill switch and she keeps running. Stop button didnt work. It scared me no lie. Reving up. Then it just stops on its own. whaaaaaaat. Thank god not on the water, couldnt stop it

 

[Jetskigoodies]

Uh oh. I hope you didnt lock up the motor. It revved like that because it was leaning out. Usually a sign of an air leak. Did it start back up and run?

 

[Jetskigoodies]

If it happens again pull the choke.

 

[Sportster-2001-951C-Stock]

Lean diesel runaway(most likely ski was lean running for whatever reason, could be empty fuel tank or air leak), sometimes it just happens if idle speed is set slightly too high. These are high strung engines, but this cannot/won't happen in the water because it's not making power when this happens, not enough power is made to overcome a loaded jetpump full of water. It can happen on the trailer only.

Check to make sure your throttle cable isn't binding or sticking and the action is smooth, look for possible air leaks(such as loose carburetor bolts), empty fuel tank? Which spark plugs does it have, too hot can also coax a lean runaway.

Pulling the lanyard won't stop runaway, best action is pulling choke to shut off air supply, or shutting off fuel supply, but choke is best choice for quickest response.

A runaway can lead to engine damage due to overspeeding.

 

[97SeadooGSX]

Yeah like I mentioned I had run it outta gas just before doing the flushing and experiencing the runaway! That must have caused it! I think i had it on the regular empty fuel line when flushing and not the reserve. This did it Im guesssing from what your telling me. I was able to restart and didnt fry it, seems ok now. WOW GREAT INFO THANKS FOR THE RESPONSE!!!!

 

[dustindu4]

It's scary the first time that happens.

 

[SabrToothSqrl]

I melted a 951 like that. removed the plug wires... didn't stop the engine.

 

[97SeadooGSX]

Yeah I guess im lucky then that I was flushing it and had water right there to cool it while runningaway and didnt fry the engine

 

[97SeadooGSX]

Funny - when it happened it was like the exhaust wasnt ruunning (audible) so you could just hear the engine - like a clear high speed whizzing sound. Scary bro

 

[Sportster-2001-951C-Stock]

Funny - when it happened it was like the exhaust wasnt ruunning (audible) so you could just hear the engine - like a clear high speed whizzing sound. Scary bro

Yeah, an unloaded 2 stroke engine with carbs on it can run "really well" on just a few drops of fuel, sorta like a turbine, and a just slightly lean one can make considerably more power than one that's getting the correct amount of fuel but the fuel cools the pistons, and it also carries the oil lubricant throughout the crankcase and into the cylinders. Running them too lean just so they are right at the power peak, on the edge of lean bogging, will lead to seizure.

This is why the high speed fuel circuit cannot be inadvertently misadjusted too lean, notice that most high speed mixture screws are set to zero turns open from lightly seated position. The high speed mixture screw is set up in parallel with the main jet so it can only add more fuel, the main jet orifice size was chosen large enough so the tinkerer couldn't tweek the fuel too lean, which they will do because if you get it just right they'll run like hell and make gobs of power for a few minutes, right before they seize.

 

[97SeadooGSX]

Wow man great info! Impressive! I need to find and read all your other posts