03 Rubicon does not want to work hard

Hi All,

I bought this 03 Rubicon used 3-4 weeks ago. Have had it out three times now. Changed the oil, put in a new air filter with no-toil oil.

It will run all day at slow speeds. Crawl around twisty trails no problem at all. As soon as I start pushing it out in the open it does not want to run. This seems to happen at any altitude.

The first time it happened the machine would start sputtering and back-firing, but never died. Yesterday heading back to the truck out on an open gravel road I was cruising about 40MPH and it would die completely. I would let it sit for 3-4 minutes and it would start up, run at 40 MPH for a few minutes and go through the same thing again.

If I kept the speed at 20MPH I had no problems at all. When I pushed it up to 25-30MPH it would not die, but would occasionally sputter and back-fire.
The guys I was with thought it was overheating (the idiot light never came on), but that doesn't make sense to me, with the back-firing and all.

Also, I have never heard the fan come on. The Polaris and Suzuki’s I was with would run their fans with the motor not running. Should my Honda do the same? (I did have the key on with the motor not running)

I love the quad, had a blast, but I was holding everyone up because the Honda didn't want to run hard!

I have never wrenched much, but would like to see if I can figure this out.

Thanks for all replies.

Man its sounds like maybe its starving for fuel. Is it carb or fuel injected?

Carb.
I will look at the supply, venting, and filters that may be installed tonight.
Thanks for the help.

jetting will most likly be your problem. Probly a leak jet.

It was starving for fuel.

I think clogged up in the petcock. Running like a champ now.

Thanks for all the help here folks!