I have a KFX 400 and love it. We mostly ride in the sand dunes at the Or. coast, bascilly at sea level. We are planing a trip to St. Anthony's Id. where the elevation is around 5000 ft. I just installed a Yoshi full comp pipe and am having it rejetted Fri. Will I have to get it jetted many times for the different elevations, or is there one set that will work? Also if it will need to be jetted more than once for the different elevations, how is it possable to jet it for 5000ft when I live only a couple of hundred ft. above sea level?
Thanks for your help in advance.

 

Factory "usually" recommends to change the main jet size 2 sizes down for altitude change of 5000 ft. If you don't, you will lose some top speeds in the range of 5~10 mph. If that's important to you, change it. If not, leave it alone for the trip. I don't change jets for trips like that because it is such a PITA to change jets on 750.

You are having a Yoshi pipe which would require a fatter jet. Now things are getting little more complicated. Your factory original main jet size is 130. What size jet are you planning to change to? Maybe you should leave it alone so that it run leaner as it is at the sea level but it would be just right at 5000 ft if you are lucky. It all depends how free-flow the pipe is. And change it after you come back from the trip.

 

I have orderd a jet kit from the dealer and I am taking my quad to the Kawasaki dealer where I bought it from. Many people say to put a 150 jet in, will that make too rich at 5000ft? Should I trust them in what they suggest? They seem to know there stuff, but that doesn't mean anything. I put the pipe on myself but as far as jetting the carb, I believe it taking it to those who know what they are doing before screwing it up my self. The only thing is they charge a pretty penny every time they touch it. I just don't want it to run like crap when we get there, thats why I asking what to do. Thanks again

 

Selecting a correct jet size for the perfect carburetion is an art of trial and error by reading the plug after several runs at WOT or close to it. Who came up with the size 150? You, your buddies, Yoshi guys or the dealer? Whoever that might be, no one would know the result for sure at 5000 ft elevation unless they tested there with the same atmospheric conditions. Like I said, if were you, I would just leave it alone and ride as it is there. You will just lose some top end power. If you are still worried, take 150 and something like 140 so that you can fine tune there. It shouldn't take more than 30 minutes on your quad. You are lucky that it is not BF750.

As far as screwing it up. It is pretty hard to screw up installing a jet. If you know how to trun the screws and know where the main jet is, you should have no problem. The hardest part is usually "getting" to the carb, and the 2nd hardest thing is "removing" the original jet (sometimes too tight - use a matching size scrwedriver tip)

 

After talking to the service Mgr. at the dealer, he says the same thing as you. There is no way to jet a carb for an elevation other than the one you are in. The 150 size jet was an idea from a buddy. When I go to Idaho I will be with a group of peolpe that have been riding Quads and sand cars for many years. This is all new to me and I just wanted to make sure. Once again thanks for all your help.