I have a 99 GTX Limited which will randomly rev to max throttle and stay there. I try to press the start stop button and pull the kill switch and it doesnt shut off. Throttle lever does not respond when this happens. I have to choke it to get it to turn off. When I start it back up it runs normal (throttle lever works, off switch works, and kill switch works) until I get about half way down on the throttle lever and then it goes wide open again and the off switch, kill switch and throttle lever do not work. Im first concerned the kill switch does not seem to work. Second the on off switch doesnt work when this happens. Third why is it go wide open? Any ideas on how to test these three issues would be greatly appreciated.
1999 GTX Limited Kill Switch
- Thread starter zano38
- Start date
Sounds like you have an air leak and a "runaway".
The air/fuel mixture is so lean it doesn't need a spark to ignite so the kill switcha nd ignition system are out of the equation like a diesel. Only cooling the combustion chamber will stop it and is hwy pulling the choke works.
Typical air leaks are the carb base gaskets and intake manifold gaskets.
On a 951 this is very common even when everything is perfect.
1. Make sure your idle is set to 2800 out of the water / 1400 in the water.
2. Never rev the engine over about 1/2 throttle out of the water.
The air/fuel mixture is so lean it doesn't need a spark to ignite so the kill switcha nd ignition system are out of the equation like a diesel. Only cooling the combustion chamber will stop it and is hwy pulling the choke works.
Typical air leaks are the carb base gaskets and intake manifold gaskets.
On a 951 this is very common even when everything is perfect.
1. Make sure your idle is set to 2800 out of the water / 1400 in the water.
2. Never rev the engine over about 1/2 throttle out of the water.
I made sure the carb is seated with new gaskets and torqued correctly. Air cleaner has no leaks. I have the high speed adjustment to 0 and I have tried up to 4 turns. Nothing seems to help with the throttle. Once it warms up and you give it a small amount of throttle it automatically opens all the way up and won’t turn off until you hold the throttle lever down and pull the kill switch. Right now I have the low speed set to about 2 turns out and the high speed at 0. Would you happen to have any other suggestions?
It could even be the pulse line,,, it is at tough spot,, and during installation of a carb,,, you can cut a small hole in it.
The hose from the pulse fitting at the bottom of the case to the pulse fitting on the carb,,, does not have a lot of “play”
Pull the carbs,, check the carb base gaskets,, and then get a mirror and strong flashlight to inspect that hose.
The hose from the pulse fitting at the bottom of the case to the pulse fitting on the carb,,, does not have a lot of “play”
Pull the carbs,, check the carb base gaskets,, and then get a mirror and strong flashlight to inspect that hose.
2strokeboy
Active Member
Id try to set the idle lower and see if your issure is resolved, also try it in the water will make a big difference
Thanks guys, I have been doing some more testing and I believe the carb gaskets are good. However when I start it up now it dies if the throttle is pressed. I have to pulse the throttle to keep it from dying and then it opens wide in its own. So based on everything recommended, my plan put it in the water to see if there is a difference. If not, next is to replace the air filter gaskets, the pulse line to the carb from the engine and also replace the crank case seal where the drive shaft goes though. It looks like I can get the oil seal out without having to remove the engine. Does anyone have any experience with this or have any tips? If all that is good, is there anything else I should look into while I’m doing all this work? I appreciate all the feed back on this one.
Air filter gasket will make no difference. The air leak is from the carbs down.
If you can get it to idle correctly you can try spraying some brake cleaner around the carb base and intake manifold gaskets and see if it changes the idle. Also as pops said it could be crank seals.
You definitely have an issue and running it in the water won’t fix it.
Could also be very lean carbs from blockages or dirt but less likely than an air leak
If you can get it to idle correctly you can try spraying some brake cleaner around the carb base and intake manifold gaskets and see if it changes the idle. Also as pops said it could be crank seals.
You definitely have an issue and running it in the water won’t fix it.
Could also be very lean carbs from blockages or dirt but less likely than an air leak
Had exact problem on 2 of my 951s both were air leaks. crankcases seams were leaking and carb manifolds on both engines sealed them up and stopped the runaway revving.
Forgot to say, had to pull engines to get to the seams. And realign driveshaft when re installing.
