johnson looper 115, how is this possible?

[nighthawk44]

I have a question to see what others think, last weekend I was working on a looper 115 belive around a 2003 model. The person was saying it wouldent Idle right but would run WOT. The first thing I did was check the fire and compression, had fire all 4 cyl's and had 145 lbs of compression on all 4. I started the engine on a flushette and it idled about 2000 rpm but sounded bad, started pulling leads off the sparkplugs but wasnt hitting right on 2 of them, killed the engine with the keyswitch then restarted it, all of the sudden the rpms went to about 8 grand or higher, went to turn off the keyswitch it it stayed running the same rpms freaked out then went and pulled off all 4 sparkplug wires, still stayed the same rpms, was really freking now thought it was going to blow up, I finally went to the carbs and held my hands over them to flood it out and it finally died, my question is how is this possible?
no spark and kill it by flooding it out!

 

[Dhadley]

Re: johnson looper 115, how is this possible?

That'll happen. The only way to stop it is to flood it. Scarey, huh?

 

[tashasdaddy]

Re: johnson looper 115, how is this possible?

it is called runaway, ( kinda of like dieseling) as long as it has fuel, it will run. 1st cause is over reving with out a load. then there is timing being off, or link n sinc being off. if you don't even know what year it is, why are you working on it. for these problems you need the proper Johnson service manual for that praticular motor.

you are extremely lucky, a connecting rod did not come through the side of the block.

 

[tx1961whaler]

Re: johnson looper 115, how is this possible?

Had a dirt bike do that to me. Started over-revving, pulled the spark plug......still runs! Flipped the choke and it finally died. Seems after a certain point it turns into a compression firing motor, kind of like a diesel.

 

[CaptRoob]

Re: johnson looper 115, how is this possible?

just curious as to what would cause this problem? sounds scary. i've never seen it happen. my first guess would be that the motor is getting hot spots in the cylinder walls that will keep it running without spark. if so what would cause the hot spots? excessive carbon buildup? an overheat that may have left some bits of piston in the cylinder walls? just guessing here!

 

[tashasdaddy]

Re: johnson looper 115, how is this possible?

actually it is over reving with out a load. timing can be off, the only way to stop, is flood, or remove fuel. i had several do it. when trouble shooting, scary.

 

[ezeke]

Re: johnson looper 115, how is this possible?

What actually usually causes the problem is red hot carbon inside the firing chambers of a dirty engine. The pistons keep pulling fuel into the engine which keeps igniting from the red hot carbon. Cutting off the fuel supply will stop it, hopefully before the engine blows up.

The two-stroke motor should not be run much higher than 1500 RPM without a load and should have a regular de-carbon treatment.

Here's a link to a good discussion of various causes of runaway: http://www.boatfix.com/how/abcombust.html

 

[noelm]

Re: johnson looper 115, how is this possible?

runaway can and does occur without any hotspots, that is what happens in a car, but a 2 stroke can have runaway by just over reving with no load, or by a very lean burn, once it starts to run lean ,remember what happens when you run it out of fuel just before it dies? and it is quite exciting huh! you are never too sure exactly what to do, but choking is about the only way to stop it.

 

[Dhadley]

Re: johnson looper 115, how is this possible?

Well put Noelm.

 

[Fltofancy]

Re: johnson looper 115, how is this possible?

Actually guys I think what you have experienced is "Free Radical Ignition". It is chemical not heat based. Since two stroke engines dont scavenge all the exhaust gases from the cylinder some gasses linger, and at high rpm it creates "free radicals", very energetic ions and cations. Google it to find out more. There is a person who has a patent on this technology and makes devices that replace the spark plugs. They are not electronic, and have no moving parts yet fire the engine right on time. I dont understand it fully, it is a strange phenomenon.

Fltofancy.

 

[clanton]

Re: johnson looper 115, how is this possible?

A friend of mine in my air force days, had a 100cc Hodaka motorcycle, that he raced on dirt oval, going down the straight away, hit kill button, this little motor would make about 3000rpms, or more then normal It would go like a rocket.

 

[tx1961whaler]

Re: johnson looper 115, how is this possible?

Actually guys I think what you have experienced is "Free Radical Ignition". It is chemical not heat based. Since two stroke engines dont scavenge all the exhaust gases from the cylinder some gasses linger, and at high rpm it creates "free radicals", very energetic ions and cations. Google it to find out more. There is a person who has a patent on this technology and makes devices that replace the spark plugs. They are not electronic, and have no moving parts yet fire the engine right on time. I dont understand it fully, it is a strange phenomenon. Fltofancy.

You wanna buy some stock in my cold fusion company?