2004.5 sportsman 400, bogs out under hard throttle
 

our sportsman 400 starts and idles great and runs good if your goin real slow.


heres the issue were having: it bogs out something terrible at wot. whats really strange is it only acts this way when really pounding on it or going up a hill. if I haven't punched it In a while or am riding on flat ground it runs like a top, tons of power for a 400. the carb is very clean. what it seems to us is the fuel pump isn't keeping the carb full and needs a rebuild or replacement. I've taken it apart as well and its clean, but the diaphragms seem like there dried out and hard.


are we on the right track here? the bike seems healthy otherwise, starts, idles real well and doesn't burn oil or coolant whatsoever.

Rare that I'd had a diaphragm bad enough to have to replace,but anythings possible.You can generally check a fuel pump out by pulling the fuel line at the carb and cranking the engine over.Should have a steady or pulsing stream of fuel. Air leaks around the intake manifold can do the same thing as it can lean one out. If a jet is partially stopped up,trash under the needle and seat,float level off,can do the same thing. If mine I'd check the fuel pump out,install a needle and seat at least or the aftermarket kit which is cheaper than just the oem needle and seat. Plenty of carb kits around for this. Plus another thing that a lot of people overlook is the clutches and belt. Worn belt,clutch parts,belt dust itself can cause limiting or hesitation.Even something as simple as a spark plug or needing an air filter change could be causing the problem.You just have to take it one step at a time with the simple things first to cross of your list.http://www.ebay.com/itm/2003-2005-POLARIS-SPORTSMAN-400-CARB-CARBURETOR-REPAIR-KIT-03-413-/370758990508?hash=item5652f53aac&vxp=mtrhttp://www.ebay.com/itm/Fuel-Pump-Fit-Polaris-Sportsman-325-500-500-HO-400-600-700-MV7-Magnum-325-330-/291550429892?var=&hash=item43e1c282c4

we actually had the bike running with the fuel line off, just idling on the fuel that was in the carb. we had a good pulsing stream while cranking and a good steady stream idling.


carb seems to be good and clean. will have to check the float level. no air leaks. air filter is clean. will likely start with the carb kit after checking out the belt and clutches and changing the spark plug. visually inspecting the belt and clutches is free and spark plugs are cheap. then go from there


thanks!

Here's the pdf fuel section from the manual that can help on float adjustment,jetting,general maintenance. https://www.google.com/url?sa=t&rct=...U2gGlaHJWSIlbA

Clutch buttons
 

Check those buttons in your secondary (or rollers if you have them) this can cause the symptoms you are experiencing. Pretty easy and inexpensive place to start.