wr 400 jetting in colorado---will it be rich?

Im new to 4 strokes so please excuse the ignorance.If im jetted ok for tx 1000ft or so and i go to colorado--8500ft est how rich will i be and do i need to rejet.Im familiar with the 2 stroke drill but this is my first time there with a 4stroke---I really dont want to rejet for 2 days but i dont want to get there and not be able to ride.A little rich might be ok but will it still be rideable? thanks for all the help i appreciate all the help i can get shane

Take your air box lid off and turn your fuel screw in a turn and ride :). Or read jetting q's and lean it out as much as possible at your present elevation. My bike runs great up to 7000, still runs better than stock at 9k. :D

I would say if your jetting is stock, you'll be very rich here. Since I don't know what your jetting is currently, it's hard to say.

8500 feet sounds like Rampart Range or somewhere similar. There are trails up to 13,000+ and at that point, I'd rejet for sure. At least bring smaller mains and you can drop the needle if the bike runs really poor.

If you decide not to rejet your bike, I suggest you bring several spark plugs with you on your ride with the Yamaha plug wrench. If you foul the plug, you need to replace it on the trail or start pushing the bike.

You can search for LarryCo's jetting and see how far off you are and get an idea of how rich you'll be running. Before I did this jetting, I was running a 160 and a 158 main depending on how high I was riding. Stock was a 165 main. It worked okay but is much better since I changed all the jets.

Good luck,


Look at my signature, this jetting works great for me and should give you aq starting point.I live at 7000 and ride up to 14000 ft.

thanks for the info--actually we are coming to salida so that jetting wiil be great---thanks for all the help--ill get these 4 strokes figured out someday shane

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