Runaway engine

Sounds like it had crud in the jets and thus running very lean. The lean condition will cause uncontrolled revs on an running 2 stroke as will an air leak.

Paw Paw

Did you drain the fuel tank? Then flush it out and make sure no trash is left in the tank. If that doesn't solve the problem it could be a bad left hand crank seal or even the intake manifold could be weather checked.

Crank seals, a runaway is cause by a massive air leak....not from clogged jets.

Cold in Beverly Hills? LOL

Remember the old 78 YZ400 I rode. Fired it up one day, and the R's went to the moon. Didn't even sneeze at the kill button.

Quickly put the front wheel against a fence post, ground it up into the highest gear possible, (3rd or 4th) held both brakes, and dumped the clutch. Would have been a good ride had it not stalled. A nice split on the underside of the intake manifold rewarded me with a mild adrenaline rush.

The only other way to kill a run away is to cut the air intake to the engine. Have had several of the older two stroke water craft run away on me as well when I worked at a small shop. Mostly due to crusty carburetors or misadjusted speed screw settings.

You could yank all three plug wires on a triple cylinder, two stroke PWC that was revving to the moon, and it would never miss a beat.

When those shit boxes would roll in for service, it only took one runaway before I learned not to fire one off on the trailer without the airbox cover off and a pile of rags handy to choke the thing off.

On most two stroke motorcycles, a crank seal will leak a bit to maybe create a lean condition, but a lot of times, the seal will be so worn that engine compression is lost, and they are lucky to even run at all.

Believe it or not hold the throttle wide open and it kills them...

Every runaway two stroke that i dealt with was caused by either a bad left side crank seal.{ causing a super lean condition}. or by a lean pilot circuit when idling. The choke worked for me to shut it off,because the extra fuel cooled the ground electrode, which was probably glowing, and igniting the fuel mixture,pulling the spark plug wire off did nothing. The worst one for me was a yamaha It400,while i was in alaska,it was like 15 below, and after i turned off the choke it revved to the moon, I panicked, hit the kill switch,pulled the plug wire and it did nothing,hit the choke and finally shut off.

^^^this^^^

IF the throttle is not stuck or physically open too far, ignition off, then this works. Active Radical Combustion,
usually called closed throttle runaway is as many have stated here a lean condition. The theory was used
in a controlled sense on Honda's EXP-2 bike, enjoy:

http://www.motorcycle.com/manufacturer/honda/honda-exp2-14293.html

Had it happen on an almost brand new 99 KX250. Turned out to be an air leak at the center cases.

Runaway motor is usually caused by a leaking crank seal. It sucks air, and runs in a super lean condition normally causing catastrophic failure...9 times out of 10 this is what the cause is...

It's a lean condition that makes it happen so base gasket , head gasket , crank seals, dirt in your carb.....any number of things could make it happen but if it went away I would think it's in the carb...dirt in your carb most likely...it's pretty difficult to diagnose a condition over the computer. If I had your bike in front of me I could tell you for certain what caused it...