- Location
- Harvey's Lake PA
So I’ve looked all over and can’t find a post about a engine runaway. So I don’t really know what it is. Is there a post that I can’t find? And what do I do to make sure it doesn’t happen to my engine (650sx) ?
Engine runaway
- Thread starter Colby
- Start date
- Location
- Stouffville, Ontario
http://www.x-h2o.com/index.php?threads/runaway-motor.111672/
Just a fyi. Its the top sticky in the Tech thread lol.
Good luck and change your underwear. Runnaway engines scare the poop out of everyone around. Last time it happened to me my carb fell off while running on the stand.
Just a fyi. Its the top sticky in the Tech thread lol.
Good luck and change your underwear. Runnaway engines scare the poop out of everyone around. Last time it happened to me my carb fell off while running on the stand.
- Location
- Coeur D' Alene, ID
https://en.wikipedia.org/wiki/Dieseling
If it happens cut airflow to the motor to stop it (put a hand over your carb(s)
If it happens cut airflow to the motor to stop it (put a hand over your carb(s)
- Location
- Cleveland, Ohio
Hand over carbs or hold throttle wide open and hold the off button at the same time.
bird
walking on water
- Location
- La Crosse, WI on the BIG River
That doesn't work all the time. I tried hands on the trumpets with my SXR...didn't work. I then opened the Choke and that killed the engine.
It happened twice with my SXR, each time I was past Reserve and started it once back on the trailer to clear the waterbox. The first time I didn't know you could just pull the throttle open. Air in your fuel lines can cause the same issue as an air leak.
- Location
- Coeur D' Alene, ID
if you have a bad airleak then covering the carbs wont always work. Drowning the motor in fuel will always work I believe, but hard to do without a primer or choke. Other than covering the "trumpets" because that cuts airflow AND drowns the motor with fuel.
- Location
- Harvey's Lake PA
Thanks so much for the replies it really helps me being young trying to learn about everything.
- Location
- central florida
So, the easiest- especially if the hood is still on- is to cut ignition and open throttle all the way. Engine will stop.
Captain PegLeg
GJP
- Location
- Villa Rica, Ga
It’s scary, but don’t panic and hold the throttle wide open. Do the opposite of what you want to do, and it will save a run away.
bird
walking on water
- Location
- La Crosse, WI on the BIG River
Pulling the spark plug wires doesn't do anything. The engine is dieseling with the ignition off already.
Pulling the throttle works every time for me. I no longer have a choke.
Last edited:
Fro Diesel
creative control
- Location
- Kzoo
Or open the throttle. Seems counter intuitive, but it has never failed to stop the motor run away.
I would NOT put my hand over the carb. Dont even want to think of what could happen it it decided to strip the skin from your palm.
Sent from my SM-G930P using Tapatalk
- Location
- Coeur D' Alene, ID
I see your point, but have done it and watched it done that way multiple times without issue. Sounds like the general consensus is just dump the throttle.
@augustaf you coming to Daytona!?
- Location
- Ontario, Canada
Something to keep in mind is that the point to opening the throttle all the way and holding the stop button will insure that once the fuel starts flowing through the carbs, it will cool the pistons preventing lean meltdown. Holding the stop button insures that the ignition system is grounded out to prevent any possibility of spark related detonation which would lead to melting a hole through a piston. As mentioned, the runaway situation is caused by a lean condition...carbs that have been dry for the duration of the off season but are getting that first start of the year can make prime lean conditions for a runaway or air leaks somewhere between the base gasket of the cylinders through to the base gasket(s) of the carbs. I've had my old 650sx do that a few times as well as a few Yamaha engines, it happens 
Midlake Crisis
Site Supporter
- Location
- Bakersfield, CA
One overlooked cause may simply be being at that point of almost running out of gas. This happened to me last week - ski ran perfectly all afternoon, I put it on the trailer to clear the water out of the exhaust it revved up normally for about 10 seconds then did the runaway motor scream. I killed it by giving it 4 or 5 pumps of the primer. Turns out the fuel level was right at the bottom of the fuel pickup, when I filled it up at home and ran it on the hose in the driveway all was back to normal.