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Discussion Starter · #1 ·
I had my 02 zr 600 out this weekend for the first time and have come to notice the sled cuts in and out on the top end. The power seems to be normal up to about 60 but then cuts in and out from there. Some times it'll keep racing up till 95/100 but other times it won't go over 80. It's not a traction issue as it's obvious the motor isn't revving as freely as it should when it's cutting out. I'm thinking it could be the apv's sticking, has anyone had this type of problem and if so, what was the fix. Other then that I was amazed at how well the sled handled, it's unreal in the twisties.
 

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Discussion Starter · #2 ·
I guess I'll reword the question...what do the apv's do? I thought I read they only should open in the higher rpm's and they help synchronize the exhaust cycle. So would sticking apv's limit the top end power of the sled? I guess the best way to explain it would be that it is seems like there is a governor when it's cutting out. It's not missing or running rough, it just seems to stop making power at around 8000 rpm/80mph. Any info would be great.
 

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APV's adjust the exhaust port size to allow for max HP at high RPM with better fuel economy and power on the low end (closed). The APV's open at a specified RPM set by the CDI (usually lower than 8000). When you start your sled have a look at the servo, it should cycle once and remain closed. If there is a problem it will cycle 3 times in an attempt to clean the valves but if the servo still senses too much resistance it will shut the system off.
There seems to be a consensus across several similar posts that your issue may be stator related
 

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Discussion Starter · #4 ·
Thanks Wayne, is there a way to test the stator. From what I've seen on posts, it seems the 02's usually don't have the stator problems as the older zr's had? Either way I think I'm going to start off by cleaning the apv valves, adjusting them, and then seeing from there. If anyone else has any other input, it'd be appreciated. Happy riding!
 

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Discussion Starter · #5 ·
Will I need new gaskets when I pull the apv's off? Is there a clear tail sign of sticking valves or would they just be gummed up? Any other tips would be nice to know when I tear into it.
 

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You should use new gaskets as they are only paper. You can make your own easy enough with gasket material from any auto parts store. Mine were actually stuck and had to be gently pried out with the help of some carb clean. There was a thread a few weeks ago that outlined how to test a stator.
 
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