MCX 240 Nytro running lean???

[Norton450]

rode my mcxpress 240 nytro at 9,000ft last weekend and it would go lean everyone once in a while. if you let off the gas and hit it again it would seem to come out of it. doesn't happen all the time, it runs great most of the time, but every once in a while when you hit the gas it will sputter and the A/F will run up to 17. it will not do it back home at 1500ft. already checked for boost/exhaust leaks. any ideas????

 

[Sleds R Fun]

Was your intake covered in snow?

 

[Norton450]

no ice or snow build up on the intake. just seems so weird that it only happens once in a while. seemed to happen more often after cruising down the trail, if I was on and off the gas in the deep powder it would not act up.

 

[TBird]

What i was thinking is that the boost line to the ECU is iceing, do you have the ECU in highest possible mounting place, and no condense water in the lines?

 

[Norton450]

I have the MCX box mounted high up on the rad. cover. i blew out the boost/vac line to it and seemed to not do it as often(i think). I am going to remove all the times and check for moisture....but again, it only does it at elevation. runs great at 1500ft!

 

[detz1000]

Is the fuel pressure holding or did it settle abit mine was doing the same thing and checked pressure and it was a little low. Turned it up and it was good and ran great

 

[Norton450]

i will check fuel pressure, but i have the stock pump.(240 kit) i dont believe i can adjust the pressure or am I wrong?

 

[detz1000]

I'm not sure I have a MSD pump and no stock one. If it has a regulator separate U should be able to adj;

 

[Norton450]

i will check fuel pressure and maybe pull the injectors and clean them. I see alot of Yamaha outboards with plugged fuel injectors and cause weird running issues. Anyone know what the fuel pressure should be on the 240 kit?
Thanks for all the help guys!

 

[TBird]

Diffrence between 240 and 270 is external fuelpump and FPR (fuel preassure regulator).
The fuelpump might be on it's way, me personally would install an external fuelpump right away even if i had the 240 kit, i heard of many oem fuelpumps loose it's capacity and lean out AFR, just a thought, hard to meassure tho without an fuelpreassure gauge.