Kickback sheered top of throttle shaft

[miket]

1987 Johnson 20HP<br />Engine running well after replacing head gasket.<br />10 hours after gasket replacement, running at very slow rpm, the motor stalls and flywheel is in reverse position (cam attached to flywheel is now positioned in rear). Luckily, I was able to force flywheel back in position and idle home. <br />This kickback has sheared plastic throttle linkage pin which connects the throttle control rod to the thottle control shaft. I replaced the plastic pin and motor ran fine.<br /><br />After about an hour of running it happened again and this time i was stranded. It not only sheered new lingage pin but sheered the top off of the verticle throttle shaft. I did notice jingling noise once or twice. I also noticed that the engine would pickup speed as though I increased the throttle.<br /><br />I have movement in pistons but can't seem to get fly wheel to stay in correct position.<br /><br />Any ideas?

 

[Chinewalker]

Re: Kickback sheered top of throttle shaft

Sounds to me like your flywheel key is sheared, which means your timing is off. The timing being off can result in the motor backfiring or kicking. Depending on how loose it is, it may also be hitting the armature plate, which is attached to the throttle arm. I would pull the flywheel, check the key and keyways (both crankshaft and flyhweel), replace the key, and reassemble. Make sure the flywheel nut is properly torqued (ask at the dealer when you order the new throttle arm).<br /><br />- Scott

 

[Hooty]

Re: Kickback sheered top of throttle shaft

When reassembling the flywheel to the crankshaft, be sure that the taper in the flywheel and on the crankshaft is clean and dry. No oil, grease, dirt, anything. Just clean, shiney and dry.<br /><br />c/6<br /><br />Hooty

 

[miket]

Re: Kickback sheered top of throttle shaft

Thanks guys. I pulled flywheel today and found damage caused by loose screws that fell out of armatur plate. Two or three screws got chopped up and even got up inside the flywheel between magnets and magneto. The magneto looks fine except for some scrappng on the support arms. I need new plate that holds spring and connection that is under magnetor which also connects to the throttle post. The key did not look damages, although there did not appear to be much of the key protruding from shaft when in place..<br /><br />I am willing to fix it if I know what caused the problem. Do you think screws came loose and created the kickbacks and damage? Or is there something else that caused the problem?<br />Mike

 

[BF]

Re: Kickback sheered top of throttle shaft

still sounds like it spun over the key to me...<br /><br />Brent

 

[SeaMasterZ@aol.com]

Re: Kickback sheered top of throttle shaft

from what I understand, those flywheels need to be torqued to 105 lbs - or is it 115 - need to be tight to keep that shearing thing from happening

 

[Hooty]

Re: Kickback sheered top of throttle shaft

The only thing the key does is keep the flywheel and crankshaft properly aligned while the flywheel nut is tightened. It's the taper in the flywheel and on the crankshaft that keeps the two of them together. That's why tightening the nut to the proper torque value is so important and why there must not be any lubricant on the taper.<br /><br />c/6<br /><br />Hooty