04 polaris no power at full throtel

Fred1956 · #1 (**permalink**) 10-21-2011, 11:42 AM

Hello to all, I bought this '04 Sportsman 400 4WD to use around the place. Previous owner said it wasn't running right so I got a good deal BUT here's the story.
PO said it was running fine and then broke a throttle cable. He replaced cable and then wouldn't run right so he sold it to me after letting it set for 6-8 months. Starts fine, idle good, power OK up to 1/4-1/3 throttle then bogs very bad. Top RPM @ 3500. I've cleaned carb, double checked carb and still no good.
Here is what I do know-
1)without air filter and air box/tube-7200 RPMs and runs great.
2) install airbox/tube- no power, 3500 RPM max
3) remove filter, leave tube/airbox on- about 4000 RPM max
4) UNLESS I put index & middle finger in the tube where air filter would mount about up to middle knuckle- then 7000 RPMs

another note, I do not have the air box top PO lost it somewhere

Any ideas ?? I used to have a full head of hair and it is slowly making it to the floor. Thanks in advance

Fred1956 · #2 (**permalink**) 10-24-2011, 08:36 AM

Posting this so that it may help someone else down the road. Deducting that it was an airflow problem that was the issue, I shopped an area salvage yard and found the airbox lid.....no more problem ! In short this ATV must be dependent on the right amount & correct delivery of air to run right. I hope this helps someone else.