I will be going to Colorado this summer and will be running around 8500 to 14000 feet. I have ridden New Mexico at 8000-11000 and the Rancher will run (Texas flatland jetting) but above 10,000 it runs weak and misses a lot at higher rpm. I have never bothered to rejet before because I have not had to. It seems like this trip will be a little different because of elevation.

My friend is bringing his 450 Honda Foreman. It did run better than the rancher in New Mexico. He will probably not rejet.

What do you think, would you do it for a trip only once a year?

If you have done it yourself on a Rancher, was it difficult. I have adjusted valves, installed my warn 424, changed fluids but never have broke in to the carb.

 

well, at the higher altitude, the engine runs richer, so it's not like you'll melt a piston or anything. The jet that has to be changed is just the main jet and the pilot screw adjustment. the pilot screw can be done without takin te carb apart, but the main requires removal. I would get a manual for your machine, it will tell you step by step how to remove the carb, which really doesnt look that complicated at all. The manual will also tell you which jet you need for the main jet, takes the guess work out of all of it.

 

Seeing how its just the one trip, id just put some holes in the lid of the air box. If you ever want it back to stock condition, the lids arent that expensive.

Put like 6, 1 inch holes. You can use a hole saw. Then go to lowes and get the 1 inch plastic plugs, and cover each hole. As an alternative you can use duct tape. Then as you go up in altitude, just start removing the plugs as needed. If removing all 6 dont get you lean enough, just totally remove the lid.

Jetting is just a term used to describe getting the fuel mixture correct for your conditions. Either the fuel can be adjusted for the air conditions. Or the air can be adjusted for the fuel conditions.

Just remember to recover those holes as you come back down to lower elevations. It wont hurt the motor to run too rich, but it will hurt it to run too lean.

 

A few years back I did run it without the airbox lid in New Mexico. It did not seem to make a huge difference. I am just concerned it will not run well at all above 12,000 feet. I am definately all for not changing the jet but I will if I need to.

 

You could call a local dealer, and ask what the jetting is for that alt. But i would think its at least 2 sizes smaller on the main. The mixture screw is also probably turned in about 1/2 turn.

None of the carburated atvs are gonna run good at that alt. They are all gonna be at a 10% or more loss of horsepower, not to mention, fighting off a too rich mixture, Its a tradeoff, and if you want it running good at that high...its gonna run drangerously lean, at lower alts. Most of us try to error on the rich side, because the worst that can happen, is it fouls a plug, or wastes gas.

Im surprised that removing the lid didnt change things dramacticly. How clean was the filter?

 

The filter was clean before I went on the trip. It is a foam filter and I use the tack spray after I clean it. My ATV has a huge power loss at altitude but it is definitely ridable, just worried about higher elevation, but I am leaning to not doing it, especially since the other ATV with me will not be rejetting.

 

that's funny, my 2005 rancher wont even rev past idle with the airbox open, i need to have the lid on to make it rideable. Must be some jetting changes Honda made in the later years.