I have 2 completely stock machines. KFX 700 and a Recon. I recently moved to an elevation of 6000-7000 feet. I called a dealer and they said to go up 2 sizes on the main jets but the local dealer told me he has had no problems with the stock jetting because the carbs are operated with vacume. Which one is correct and if so, what size jets should I run in each. Thanks.

 

Here is what I do. My bikes are jetted for sea level. On the bikes that I ride in the mountains (Ranchers, 250EX, Recon), I have two TPI valves (http://www.thunderproducts.com/tpi_valve.htm) installed in the airbox lid. When I am in the low desert, I have the valves closed. As I ascend in altitude, I open the valves to get more air to compensate for the altitude. By the time I get to 10,000ft., they are wide open. Above that, I just pull the airbox lid off completely. It's a system that works very well, and you don't have to be rejetting all the time!

If you are just going to ride in the mountains, then get a rejet. Your bikes service manuals will tell you what to do. If you are going to also ride low desert, high desert, Glamis/Pismo, etc., you should give the TPI valve a try.

Looking of folks to ride with??? We have a group of riders from the local area. Several live in the Running Springs area (two of them, "Wiley Coyote" and "Happy With V-Force", ride KFX 700's!). PM me if you are interested. We are doing a Glamis day ride on the 19th.

 

easiest way to compensate for altitude is with a Dial-a-Jet.

RR, sounds kinda backwards. At high altitiude, the air is thinner, and you need less fuel to maintain
the optimum air/fuel mixture, which is 14.7 to 1 (I believe). You are adding more air at higher altitudes,
with the same fuel. Unless you have a high flow air filter, those TPI vavles are making no difference
anyway.

MacV, everything I have seen, read, and heard about changing altitudes involves smaller jets, not larger.
Sounds like the furst dealer you talked to has no idea what he is talking about. The Honda manuals all talk about smaller jets for higher altitudes.

 

Guys, it takes 5 minutes to rejet the main on most quads. No big deal.

 

The second dealer was right..to a point. CV carbs are self regulating, thats why the needle doesnt need to be played with, just the main jet, and i agree, they need to be smaller, not bigger. If you find yourself at altitude and didnt jet yet, removing the air box lid will do the same thing. It leans the mixture out.

 

if you dont rejet it, what will happen, besides running crapy

 

WoodsRunner-The TPI's work great! You are adding more air VOLUME, to make up for a lower air DENSITY at altitude. (It's the same company that makes the Dial-A-Jet, which I have not tied yet.)

MacV has a special case here. He lives in the mountains, but has great riding all around him at lower altitude (even below sea level!). So he would be rejeting every ride.

I have the opposite problem. I live in the valley, and I ride up into the mountains. I can have an altitude change of 8,000' IN ONE RIDE! What am I going to do? Stop and rejet twice during the ride, out in the dust and dirt??? That would be ridiculous!

 

So I will be OK if I go for a couple hour ride this weekend before I install the TPI's? Just wanted to make sure I was not going to hurt anything by not rejetting.

Thanks for all the feedback.

 

reconranger, If I was in your situation, and I wish I was, Id do the same thing....its the easiest and quickest and cleanest way. The motor doesnt care if less gas comes in or more air comes in.


MacV700, If you see black smoke in the exhaust, or it starts running crappy, then youre running rich, at that point, stop and remove the air box lid, and you should be fine. Running rich wont really hurt much, there arent any catalitic converters on quads, its just runs a bit crappy and uses a bit more gas than it should. Running lean, is another story, you dont want to do that. Heres an article on jetting, and it lists the symptoms, of running lean and rich. [ L=jetting]http://www.motorcyclecruiser.com/tech/jetkit/[/L]

 

One caution about the TPI: You MUST remember to close the valve back down when you descend in altitude. If not, you will be running LEAN, which will make the engine run hot, and can damage the engine. You just have to be on your game if you use it!