Author Topic: 08 KX450 SHEARED FLYWHEEL KEY  (Read 2475 times)

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Offline ThrottleJunky

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08 KX450 SHEARED FLYWHEEL KEY
« on: April 27, 2011, 12:29:29 PM »
I stalled my bike in a turn and couldn't get it restarted.  I thought I flooded it while trying.  Took it home and tried to start it again but couldn't get it to fire off. Checked all vital signs and found the timing off a small amount. Timing kept moving so removed the flywheel and found the woodruff key sheared.

Anybody ever heard of the 450's shearing keys and why?

Thanks!
TJ
'There's more living in five minutes flat-out on a bike than some men have in an entire life'.

Offline Friar-Tuck

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Re: 08 KX450 SHEARED FLYWHEEL KEY
« Reply #1 on: April 27, 2011, 05:52:10 PM »

  TJ,
 Although I haven't spent a whole lot of time with newer 4 strokes, the 500's have a reputation for snapping them.
  Why they snap may have to do with the fit of the tapers of the flywheel and crank.
The only remedy I read about was to lap the two mating surfaces.
   I used valve lapping compound and lapped the flywheel to the crank.  I didn't get crazy, maybe 5 min.  Turn by hand back and forth.  The idea is to get the High/low spots out.   Clean  everything well before reinstalling.
  Tuck\o/
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Offline jonny500

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Re: 08 KX450 SHEARED FLYWHEEL KEY
« Reply #2 on: April 27, 2011, 08:23:41 PM »
+ 1 this works well, listen to tucko he know his stuff :-D

Offline ThrottleJunky

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Re: 08 KX450 SHEARED FLYWHEEL KEY
« Reply #3 on: May 02, 2011, 10:38:07 AM »
Thanks for the info!

I did a light prussian blue check to be sure the taper contact was good before installation. I read about 90%. I will put a light lap on it before reassembly.

I haven't sheared a key in a flywheel since the early 70's!  I had about 15 total minutes on this engine.

Back when I was building this bike a 9 oz. Stealthy flywheel weight popped up on Ebay and I couldn't resist.  I'm thinking about the effect of the extra weights' inertia has upon stalling the engine. This may have something to do with it. 

I ordered 3 keys so if it happens again with the flywheel weight, it will be coming off! 
'There's more living in five minutes flat-out on a bike than some men have in an entire life'.