Comments on: ATV Jetting

By: Nick

Nick — Sat, 28 Jan 2012 22:13:12 +0000

Hi Robert,

I doubt you’re going to need to adjust the jetting on that particular engine with those performance mods if the altitude isn’t changing. The air to fuel ration, which is roughly 12.5 to 1, will still be the optimal mixture. Make sure you run on the rich side if anything, a lean condition will burn out your engine and you know you’re lean if you get backfiring and slow response. Rich isn’t better, it’s just less dangerous to your engine.

By: Robert

Robert — Tue, 24 Jan 2012 19:37:28 +0000

2008 525 S, Outlaw. I’m installing FMF power bomb and factory 4.1 exhaust. I’m also thinking about running 105 leaded fuel, the elevation I’m running at is round 5,000 ft. Operating leaded fuel and new exhaust how much will that effect my jetting? The jetting right now is working fine.

By: Nick

Nick — Thu, 21 Jul 2011 06:42:14 +0000

You didn’t mention the year or details about exhaust upgrades etc. In my opinion you may not need to rejet at all for the trip. I’ve had stock ATVs (2009, 2010) perform equally as well at 8500 feet as they did at 2000 feet. You won’t be riding at high altitude for long and would have to rejet again when you came home. Your best bet however, to be on the safe side, is to get an ATV jetting kit before you leave and have it with you on the trip. Follow the manufacturers instructions about high altitude jetting adjustments if you feel that the ATV isn’t running properly and if you end up not using the kit consider it spare parts for later. I don’t think you’re going to need it and it doesn’t take very long to make the change if you do.

By: Tony

Tony — Wed, 20 Jul 2011 01:17:01 +0000

I’m going out west to hunt in the mountains. 7,000ft, what jet factor do I need for my suzuki 500 vinson? Thanks

By: James

James — Sat, 23 Apr 2011 01:03:23 +0000

Wow, thanks for this, I wish I found this a long time ago. Now ill go look for my jet settings.

By: Cliff

Cliff — Thu, 15 Jul 2010 17:12:17 +0000

After installing a pipe and free flowing filter to my son’s 300ex, I used the recommended jetting by the pipe mfgr. I’m getting a stutter on the top end. I dropped down the main jet size and lowered the needle and its still doing it. Am I going the wrong way? Do I need to go bigger on the main jet or raise the needle? Thanks,

By: Nick

Nick — Fri, 24 Apr 2009 21:02:36 +0000

Hi Jason, lets assume your current setup is jetted for sea level and the temperature is 60 degrees F and give that a rating of 1. Now, take that rating and move it up to 3000 feet, same temperature and you’re looking at a jetting factor of roughly 0.97. Next bring it up to the 5000 ft mark, same temperature, and it would become roughly 0.95.

What those ratings mean is that if your main jet at sea level was a 180 you would multiply that by 0.97 for 3000 feet and 0.95 for 5000 feet (temperature matters, colder=higher factor).

If your jet is 180×0.95=171. You’d be replacing the 180 with a 171 main jet at 5000 feet, replace the 180 with whatever jet you’re using in that equation. Hope that helps.

By: jason

jason — Thu, 23 Apr 2009 01:01:15 +0000

We are heading to St. Athony dunes in december and my quad is jetted for 0 to 3000 ft. elevation. How many jet sizes should i drop to run at 5000 ft.? Thanks Jason

By: Nick

Nick — Mon, 06 Apr 2009 09:45:38 +0000

You’re welcome!

By: BrentTRX

BrentTRX — Tue, 04 Sep 2007 03:52:07 +0000

Thanks for the advice!