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I've got a 2009 Grizzly 450 down on an island here in TX, so right at sea level. We're planning to boat it back across the bay and up to Colorado to assist with an Elk hunt this November. Obviously quite a bit of altitude gain. Right now she requires a little choke or just a heavy throttle thumb for a minute or so until she warms up then she'll idle fine. I'm thinking between the altitude and the MUCH colder temps I need to pay attention to the carb to be sure she runs smoothly up there. I don't know too much about carburetors so figured I'd ask here and see what's recommended.
 

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I've got a 2009 Grizzly 450 down on an island here in TX, so right at sea level. We're planning to boat it back across the bay and up to Colorado to assist with an Elk hunt this November. Obviously quite a bit of altitude gain. Right now she requires a little choke or just a heavy throttle thumb for a minute or so until she warms up then she'll idle fine. I'm thinking between the altitude and the MUCH colder temps I need to pay attention to the carb to be sure she runs smoothly up there. I don't know too much about carburetors so figured I'd ask here and see what's recommended.
Ridgway is in CO and has experience with his carbed 660 at altitude. You might seek him out.
 
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Ridgway is in CO and has experience with his carbed 660 at altitude. You might seek him out.
@wgc is also a regular on here and can help with that too.
 

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screamingpotato- I don't know squat about a 450 but I'll provide you with a little info. My 2004 660 came with a 145 Main Jet (Factory) and I replaced it with a 140. Other then the loss of performance due to altitude the thing runs real well. I've been to Moab and above 13,000 (same jetting) and she runs real well. I didn't change any thing else. I just called my local dealer, who I've dealt with for 50 years and trust, and talked to the Shop Supervisor. His comments were that most people don't mess with them. However he did tell me, after looking up info for a 2009 450 Grizzly, that the stock jet should be a 131 and you may want to go to a 125. His only other comment was that you may have to turn up the idle a hair and give the idle circuit screw a 1/2 a turn in.
The only other thing would to mess with the needle slide clip (up or down) and your not going to be able to do that until you are actually here at altitude and see what your machine is doing. That's actually a pain in the a$$ and I would probably forgo that. I live here year around so I've played with mine to optimize it. In your case your here a week and it should run well without having to adjust everything. One thing to note is if you do change the main jet (to a 125) don't run it at sea level because your going to make it awful lean and may cause harm to the motor.
General rule of thumb for us, at altitude, is that we use a 8% difference (from stock) to get us in the ball park and tune from there. Your better to run it a little richer, then leaner, hence the recommendation of the 125. That's providing you feel the need to change main jets. Good Luck
 

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Wow thank you, never expected that much info! I need to swing by and bring you a cold beer when I'm up there. I'll be saving this info for sure, might order the parts and head up and see how she runs and install there if need be. We are going up a few days early to allow this flatlander to acclimate to the altitude before engaging in any strenuous activity so I'll have opportunity to work on it first.

I'll be running around at 8000-9000 feet most likely and will spend most of my time on foot. Game retrieval it seems I'm allowed to make two trips up to 1 mile off trail so that's why I'd bring it. Packing out an Elk on foot having one less mile to haul will help assuming I can get the ATV through the terrain.
 

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screamingpotato- One of the things that I forgot to mention was the fact that you were Elk hunting, generally by then the high country is closed due to snow and figured you be at 10,000ft or below.
My recommendation, based on what I got from my dealership, is to give it a go as is and just change the main jet if you feel it's necessary. When you get to Colorado just take the Grizz out find a open road and wind her up, full throttle to 40-50mph. If she's not blubbering at full throttle I'd say your good to go. If you feel the need to change out the main jet you should just be able unscrew the big major bolt under the float bowl and remove the main jet (think it's around 6mm) and swap out. Think main jets go for around $6. Your going to be down on power just because of the altitude and their is no way around that.
Enjoy your trip, dress warm and hope you get a 5-6 pointer.
 

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Yup, at a higher altitude, there is less air so you will need to drop the jets to run leaner as said. The main jet is gonna be your issue when 1/2 to full throttle. At idle it does nothing. At idle you will want to screw the air screw in a little to lean it out. Drop the needle jet if you need to, but with the other two adjustments you should be fine.
 
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