Kick starter randomly locking up?

Carpenter321
Edited Date/Time 2/25/2016 12:25pm
This is my first post so sorry if this has already been discussed before but I couldn't find anything.
So I recently got back into riding after a 7 year layoff and picked up a 2009 YZ450F. I have taking it out 3 times in the last month and it runs strong the only issue is once or twice each day I go to start it and the kick starter wont move. I let up on it and it kicks right over. I have never had a bike do that but I have only had 1 other 4 stroke, a 2005 YZ250F, and it was only for a year. Is this something I need to worry about? What do I need to check? I would rather tear in and fix a small issue before I blow the motor up because I dont have the 2K+ for a new motor.
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NHtoWA421
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Bremerton, WA, USA
NHtoWA421 2/24/2016 7:20am
2/24/2016 7:20am
Sounds like it's just locating TDC maybe?
Falcon
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Falcon 2/24/2016 10:39am
2/24/2016 10:39am
If there are no other issues (stalling, seizing, horrible sounds,) you are most likely experiencing the huge compression advantage that a 450cc 4-stroke employs at BDC or somewhere upward of that on the compression stroke. Short of unscrewing the gas cap and rolling a 250cc 2-Stroke underneath it, you can't fix that.
Modern 4-strokes have an automatic decompression release that should be working in this scenario, so you may want to have it looked at. Otherwise, just return the kickstarter to the top and slowly kick it past that point in the stroke then return to the top and kick.
T-MAC
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T-MAC 2/25/2016 12:25pm
2/25/2016 12:25pm
I had a similar issue on a 2007 rmz 250. It "locked up" occasionally, which resulted in cracking the case behind the kickstart assy. In this bike specifically the kickstart idle gear is only supported from one side (the inside). The kickstart idle gear sits on a dowel of sorts that is just a slip fit into the inside case half. This interface had a little bit of play, and there is a ton of force on this point (the force of you kicking the bike). This actually slightly cocked the kickstart idle gear to the point where it would catch the primary drive gear on the back of the clutch basket and lock up. I ended up getting a new kickstart idle gear and shaft that it sat on and actually machined a chamfer onto the outside edge of the gear so it's less likely to catch the primary gear on the clutch basket.

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