Can't make mcx 240 kit run right.

[jasonrev]

My buddy has a 2011 nytro with a 240 mcx kit that he can't get to run right. Down the trail he can punch it and it pulls boost and works good. When you get into the snow and make it work a little harder it sputters and pops. Seems like it running lean. The motor has been gone through, it has new aux injecters and PG yamaha has looked at the mcx box. The fuel pump and filter has been changed and the vacuum lines and tees have been checked. Anyone have any suggestions to make it run right?

 

[up-high]

How much boost does it make on the trail? If not what it's supposed to make I'd start looking for boost leaks.

 

[sledheadd]

My 270 kit was doing this once, turned out the exhaust bellows were blown out. I'd imagine that PG would have checked them though.
I'm guessing a leak somewhere.
Have you done a leak down test?

 

[Climbmax]

does it have a fuel regulator? If so I would be suspect of that. Had a 270 kit do something similar. But I forget if the 240 kit had regulator.
Good luck

 

[BBNytro]

Cracked header and/or exhaust leak. Seen the exact same thing last season.

 

[Thistledoo]

if you need the copper donuts for the exhaust I have a few left...pm me