To jet or not

[chevyman89]

Should u jet a 4 stroke for the winter time or no. I have a buddy with a raptor and he didn't jet for the winter and it ran fine. And other buddy with a Preditor jets his bike for the winter. So do u jet a 4 stroke for the winter or not?

[Rip_Tear]

I would say you don't "have to" but it would run/start better if jetted correctly. In the winter the air is less dense and you will be running rich in the air department.

[chevyman89]

Thanks man anyone else

[trx400EXtreme]

i would jet it. it will run way smoother.

[GPracer2500]

Originally posted by Rip_Tear
....In the winter the air is less dense and you will be running rich....

Backwards. Cold air is more dense than warm air. Dense (cold) air needs more fuel (larger jets). Thin (warm) air needs less fuel (smaller jets). If you are jetted correctly for 90 degrees, at 30 degrees you'd be leaner than ideal without changing the jetting. Also, cold air holds less moisture than warm air and dry air needs richer jetting. Humidity doesn't play a huge factor, but if you're trying to get spot-on with your jetting it should be considered. One jet size (i.e. 160 to 162 or 162 to 165) is appropriate for every 25 degrees in temperature change. That's approximate but close.

Unless you have huge swings in temperature during the year, it can work out ok to jet so you're a little rich in the summer and a little lean in the winter. You can only be just right within a certain temperature but that's fine for most people. What you don't want is to be a tad lean in the summer and then not richen the jetting for the winter. That could make you way too lean in the winter.

[chevyman89]

Thanks is there anyone out there with other idea

[CarGuy7a]

GPracer2500 pretty much said it all. how else would hot air balloons float. because hot air is less dense than cold.

the way i jet mine is i get it a tad richer than normal for the summertime then it's spot on for winter time. that way i'm not constantly re-jetting.

[chevyman89]

Thanks guys for the help

[Rip_Tear]

Sorry about that... I don't know why I put it was less dense...