Hi all.. I have a 2014 Zforce 600EX with approx 250 miles on it.  It used to get up to 50+ mph...now the best I can do is about 37mph.  I just cleaned the air filter again and that didn't help!!!  Not sure what else to do so any help would be greatly appreciated...

Thanks!!!

[2015 Z Force 800 53/Trail EPS]

Some that report this kind of issue find an issue with their belts as in they have lost their guage...ie the width of the belt has changed due to incorrect secondary clocking for the changes in loads or terrain they have been running in. It's easy enough to check. Just pop the cover, mic the width and compare to the spec in the service manual. Belts also stretch under prolonged loading and especially when very hot...and these do get hot. This also effects shiftout ratios.   

While you have the cover off, check for dust build-up in the clutches. The z6 doesn't have any sort of filter on the cvt.