Suggestion for altitude jetting on old wr400

[WaterKid]

I have a 2014 St timbersled on an older wr400 and having a blast on it. (My sled is for guest only now). But recently its been cutting out a full throttle, something that I rarely do on dirt but now its much easier to tack it out especially on powder hills.
Anyone have any suggestions for what I should have my carbs set at to avoid this?
It always happens when i need the power most. This is my first time running my bike at 14 deg at 4-7000 ft.

 

[M5-]

Its not likely a jetting issue at full throttle and 14 degrees you are likely starting to see carb icing.

M5

 

[WaterKid]

Carb ice

Thanks for the tip, I will research that issue out in more detail.
My air box was clean and not iced or even frosty inside after the ride.

I'm assuming the buildup is inside the carb housing?? so building a enclosure of sorts should help both protect and create a heat box for the carb. I heard that 2 strokes are prone to this but mine is of course a 4.

 

[tahoesldr]

I have a carbed YZ250F and installed a fuel screw over the summer. That's been a huge help for me. What I've found is that I need to run it richer initially to get it started when cold and then lean it out when it warms up. I was initially getting some bogging when giving it throttle, but after leaning it out the bogging went away.

 

[cokecrazed007]

I have an Holzman attack system on my carb and I have no issues with temp and elevation.

Sent from my SM-G900W8 using Tapatalk

 

[WaterKid]

Found it was carb ice afterall

After letting the bike sit for a few days in very cold weather I found the ice in the carb had set so hard it was preventing the choke and hot start levers from moving.

After warming up the whole bike and letting it run it cleared up the problem of cutting out at full throttle.

Guess I'll be building an enclosure after all for the carb area. I think I'll use some aluminum sheet metal. Any one else find something that works better?

 

[Corban_White]

I believe it needs to be fabric or plastic, something that conducts less and will not allow snow to stick to it. I used industrial vinyl. Works great.

 

[M5-]

You will need a real engine coolant based carb heater not the crappy KTM electric one. Avid makes one or you can have one made at a machine shop. Do a search on this forum you will find lots of info and pics. All the carb guys have been around the block on this one its the only decent solution which actually works.

M5