i need to know what jet to put in my 2005 honda 450r. and my 2005 polaris sportsman 500 ho. right now i am at an elevation of 1100. i plan on going from around 4000 to 14000 in the mountains. if any one could help, it would be greatly appreciated.
my honda 450r has k&n air filter and yoshimura pipes.

 

My typical mountain ride goes from 4,000' in the valley and end up over 11,000' (all in one day's ride), and here is how I handle it without rejeting! You can rejet by decreasing the amount of fuel, or you can increase the amount of air...I choose to keep it simple and increase the air!

I leave my jetting alone. I put two Thunder Products TPI Valves in the airbox lid (they are very inexpensive). I open them as I ascend to get more airflow, and then close them when I descend to decrease the airflow. Above 9,000', I just pull the airbox lid off completely. (Do be carefull on deep stream crossings however.)

It's a system that works very well! Don't make things any more complicated than they need to be! http://www.thunderproducts.com/tpi_valve.htm

 

The problem I was going to point out that you may run into is that you have a BIG altitude change from 4000 to 14000. Any jet you put in will not be suitable after a few 1000 feet. Example: a jet for 5000 will not be suitable for 8000 or 9000. You would have to rejet on the spot! The method reconranger suggest is ideal. It will take care of that problem.

Point reconranger.

 

If you feel like you must rejet, you will have to rejet for the lowest altitude where you will ride on your trip (4,000'). If you return below that altitude, you will be lean and may damage your engine. If you start out at 4,000' jetted for 10,000'...you are going to toast your engine!

Jetting is art not science! You change something, take it for a ride and see how it does. You want to do that all day out on the trail, rather than enjoy the scenery? It usually doesn't work to just pick jet sizes out of a manual anyway. While it is easy to change a main jet, it's way more difficult to get the needle and other jets just right.

 

The TPI looks like a great product and the website is pretty intuitive. Just wondering how many I would need to run on my airbox. they have sample pics of some airboxes but they all have multiple TPI's. Just wondering what would be the best setup for me riding at around 1200 ft.

 

On a 400EX lid, you could probably fit at least 3. I only have them on the Rancher 350 (the 420 is fuel injected). I don't typically ride the EX or R at extreme altitude.

I can't fit the TPI's on the 250EXs, because they go to deep down into the airbox and would hit the air filter. So, on those I have to do it the old fashion way. I cover the lid with a bunch of UNI round air vents, and do the duct tape on and off thing.....