Yz450f spuddering when it gets hot?

I was riding one day turn the bike off in middle of trail for a break.. Kicked it like crazy ended up pushing it a mile through a equestrian center wher I wasn't supposed to be.. Anyways after that I replaced the coil and stator and the bike would start it would run fine for about 5-10minutes when it got to temp or hot it would start this spuddering.. When you crank the throttle it dosent want to raise in rmps and make this repative noise.. I was told it could be the cdi box "brain box"??? Has anyone heard of this problem anything like it?

If it "sputters" when hot, and it's an electrical problem, it's rather more likely the stator is faulty.  The CDI's are pretty robust, and don't often fail.  A check of resistance values per the manual while hot might show it up right away.  If not, try tapping on the outside of the flywheel cover area while testing.

Thanks for answering... The stator is brand new yamaha part.. How do you do that type of test on the bike?

Details are in the manual.  Have one yet?


If not, look at the top of the index in the YZ450 forum, open "Common Threads", and go to near the bottom of the second post.  There's a link to real, free PDF manuals from Yamaha.

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