Last evening I did some riding/testing last night since it's the coldest it has gotten since I picked my rancher up in the spring. Anyway it's definately a little slower/weaker when cold ( it was at 30 F, 45% humidity.) I was going to pick some minds on how to restore a bit of power. I assume the motor can never come up to full tempereture when cruising at speed, that would indicate richen the mixture(a jet size or two up.) Perhaps the stock air filter soaked with FFT may cause the thicker air to slow down more, (air starved, maybe even rich mixture-replace with the K&N?) I'm already running colder weather oil, 10w30 synthetic.

Any help would be appreciated.

 

You've got the right idea. As air cools, the molecules become more dense, as the heat that normally excites them is no longer present.

So, the oxygen, part of our air, also becomes more dense. This will cause a lean condition in your motor. Actually, when the motor leans out - you get a hotter running engine, because gas is the main source of cooling - since your lean, it'll run hotter.

Normally, four stroke engines are quite forgiving regarding jetting. But Hondas are different. Honda carbs run on the lean side (helps with emissions), that's why you are seeing a lean condition, where normally you wouldn't notice.

I would bump up the main jet two sizes above the stock jet. I think that'll correct the lean condition. And since Hondas are normally lean, you can probably leave that size in year around. You'll know if it's too rich, the quad will blubber and have a hard stumble with acceleration.

Also, if you want your quad to start and idle MUCH better, turn your air/fuel screw about 1/2 turn out (it'll richen your idle circuit). It's located under the carb, right in front of the floatbowl. Make sure to turn it in the correct direction, as it's upside down. Honda has jetted the idle circuit lean as well, that's why Honda's are called "cold-blooded." This 2 minute adjustment will make your life much easier (with cold starting).

ogre