2015 Xc 300 midrange flutter/stumble

Related:
Create New Tag

7/7/2017 4:37 PM

I"m stumped with a problem my Xc 300 has developed. I"ve had this bike since new & have the jetting down pretty good. Last few times I have ridden the bike on an MX track, it is stumbling in the mid range, not a full on bog but it's fluttering before it starts revving to the top end....never did this before. Clean & crisp off idle & on very top end...I assumed reeds were bad, checked them and they look good. Carb is clean, fresh fuel, clean air filter...new plug, .changing jetting does not make it go away...motor is stock, Oem top end replaced about 8-10 hrs ago..Any suggestions?

|

7/7/2017 5:22 PM

Power valve?

|

7/7/2017 5:38 PM

CSAR FE wrote:

Power valve?

Going to have to dig into this thing a little deeper......has good clean bottom & top end, can't hurt to pull a cover off side of cylinder & manually operate the valve....thought for sure it would be a frayed or broken reed, but they look like new. I"ll check float height & needle valve also... Weird condition, I come out of a turn good throttle response then starts getting into midrange & it flutters for a second or two, then cleans up & rev"s out to top good....

|

7/7/2017 6:04 PM

I would reconfirm the Z dimension. The screw may have come loose and the power valve might be misadjusted.

|

7/9/2017 1:46 PM

I had and have the same experience on a 2012&2014 250sx that both always had the same issue although not as pronounced on the 2012. I have tried 2 different OEM carbs and a 36mm lectron on each. Tried all different jetting on OEM carbs and equivalent strategy on the lectron. Never solved the issue. Problem existed since new and after Reed replacements, so it's likely not that.

|