Sand Dune jetting 06 yz450f

[Luigic81]

Will be my first time with a 4 stroke in the dunes, do I still need to jet richer on the main like I would do on my 2 strokes? I don't plan on changing the needle position nor the pilot jet (other than richening the fuel screw) I'm running a 165 main now, what should I run for the dunes? 170? 175? thanks!

[mkporn]

what temp you going to ride at? Is your bike spot on right now? Is it a bit rich right now? there are a lot of things that will determine this, but simply put if you ride in the area already and the temps are around the same as normal and your bike is on now, you will be fine. If you are very concerned just bump one size on the main if your jetting is good now, but realistically you will be fine with what you have unless temps change drastically and you are coming from a higher elevation.

[grayracer513]

If the bike is jetted right now, there's no reason to rejet for the dunes, unless it's going to be a lot hotter, or a lot lower altitude, in which case you might go one step richer.

[Luigic81]

Bike runs excellent now, it ran pretty good with teh 170 main, but when I put in the 165 is pulled ahrder on top and was crisper. it will be about 20 degrees cooler where I am riding, but the same elevation. I've been riding supermoto here and its been like 80-90 degrees, the coast is supposed to be around 62 this weekend I believe, so ill probly throw the 170 back in just to be safe.... or maybe a 172 if I have one laying around

Thanks guys

Edited July 29, 2010 by Luigic81

[STROKEDIESEL]

its hot outside here and there(oregon) i'd go 168 or 170 personally!!!

[Luigic81]

its hot outside here and there(oregon) i'd go 168 or 170 personally!!!

yea but it looks like the coast is a good 20-30 degrees cooler than here in portland. I'm sure a 170 will be fine

[grayracer513]

its hot outside here and there(oregon) i'd go 168 or 170 personally!!!

Heat, like altitude, makes any given jetting behave richer because the relative air density goes down. I run a 165 in the warmer months and a 168 in the winter in the deserts here.

The thing about having to run richer when it's hot is a holdover from two-strokes, and air cooled two-strokes in particular, and really has more to do with the fact the oil is carried in the fuel than it does the mixture. The problem could just as easily been dealt with by increasing the oil in the fuel mix.

The whole thing doesn't really apply to four-strokes that much, and is a bit of a myth overall.