Kick start arm keeps breaking, HELP.


5 replies to this topic
  • CR2CRF

Posted December 08, 2012 - 07:48 AM

#1

My buddy has a 2009 YZ450F and his kick start arm keeps breaking right at the pivot knuckle. Here is a pic of his sixth one. After the third, Yamaha stopped giving him new ones.

So here is his routine and how they break. Bike starts cold as usual. No problems. Then, when it's warm, and he is as far away from the truck as possible, he stops to take in the view. When he goes to start the bike and pulls in the hot start level, he says he gets a compression type kick back and wham, that small piece flies off. Now the kick starter is useless. That little knuckle keeps the starter from flipping back towards that back of the bike.

Can this starter be swampped out with another year/model? Any ideas?

Posted Image

  • Methotic

Posted December 08, 2012 - 02:02 PM

#2

Maybe the auto compression release is not working properly. You shouldn't have to kick it with enough force to break a kicker like that. The timing may have jumped and is causing the auto compression release on the exhaust cam to fail. Make sure your cams are lined up good and the timing chain has good tension.

  • CR2CRF

Posted December 08, 2012 - 04:40 PM

#3

I'd like to agree but it's been happening sionce the bike was new. But I will see if he can bring it by so I can look at it. I am sure he has no idea what you just said. And I have seen things like this happen from the factory.

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  • grayracer513

Posted December 09, 2012 - 09:22 PM

#4

If it kicks back that hard, I'm surprised it hasn't hurt him. Wear boots when troubleshooting.

This sounds like an ignition timing fault. Too advanced when cranking. Timing is controlled by the CDI. It uses the signal from the pickup coil to determine crank position and engine speed, then looks at the TPS for throttle position as a way of determining engine load. If any of these components are faulty, it could cause this.

If the flywheel key is sheared or displaced, that could do it, too.

Then again, he might be causing his own grief if he's twisting the throttle open on an engine that isn't flooded.

  • peaceofwork

Posted December 10, 2012 - 12:20 PM

#5

2 stroke guys love to blip the throttle when kicking and that makes a 4stroke kick back

  • CR2CRF

Posted December 10, 2012 - 05:25 PM

#6

If it kicks back that hard, I'm surprised it hasn't hurt him. Wear boots when troubleshooting.

This sounds like an ignition timing fault. Too advanced when cranking. Timing is controlled by the CDI. It uses the signal from the pickup coil to determine crank position and engine speed, then looks at the TPS for throttle position as a way of determining engine load. If any of these components are faulty, it could cause this.

If the flywheel key is sheared or displaced, that could do it, too.

Then again, he might be causing his own grief if he's twisting the throttle open on an engine that isn't flooded.


He says it starts cold fine. Like first or second kick. But warm is abeast to start and uses the hot start but then the kick back and wham! Broke again. This is since brand new.





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