Stuck in mountains PLS HELP

[BO4RE]

I drive a 2004 rx1 mountain

151 track
stock clutch
aftermarket air filter

160 jets 6000 feet aparently

Heres the problem. Driving the sled at the parking lot at the base of the mountain, everything is perfect. After riding the 30 km trail and arriving at the Alpine she starts farting and burping after 7000rpm. I checked the plugs , they were a nice light brown totally dry. So I fifgured she is not running rich. Couldnt figure it out all day, rode down and about 15 km down it basicall sorted itself out full power al the way to arounf 10,000rpm. I have owned the sled for 3 days and have no idea what the problem is, the owner seemed like a good guy and is trying to help me out, could it be bad fuel ??? Anyway so yeah, no power above 7000rpm it just burps and sputters, pls help

 

[alterhi]

If you look farther down , there is a RX Mountain forum. Better answers there I would bet. I probably have never been over a 1000ft.
Sad, but it's all we have.

 

[Turbo Tim]

160 is way too fat for 6000 feet

 

[rx1mtn]

I would jet to 132.5 maybe even 130. 130 is what I run at 8000 ft. Make sure the secondary is twisted to at least 70 degrees. By stock clutch, do mean it has O-S-O spring and not rivets in the weights?
Good luck

 

[snowbeast]

I drive a 2004 rx1 mountain

151 track
stock clutch
aftermarket air filter

160 jets 6000 feet aparently

Heres the problem. Driving the sled at the parking lot at the base of the mountain, everything is perfect. After riding the 30 km trail and arriving at the Alpine she starts farting and burping after 7000rpm. I checked the plugs , they were a nice light brown totally dry. So I fifgured she is not running rich. Couldnt figure it out all day, rode down and about 15 km down it basicall sorted itself out full power al the way to arounf 10,000rpm. I have owned the sled for 3 days and have no idea what the problem is, the owner seemed like a good guy and is trying to help me out, could it be bad fuel ??? Anyway so yeah, no power above 7000rpm it just burps and sputters, pls help

whoes air filters was he using,if it is freddies give him a call,he will most likely tell you that you are to fat,i ran his kit at sealevel with 160 and 165s and it was plenty,so my gut feeling is you are way to fat for that elevation,i dont think i would go down to 132.5 or 135s maybe 140s or alitlle larger,but try the 140s and see,at least they would work at say 7000 dont know about up to 10,000 feet???