I have a 2002 500 sportsman. I was out riding yesterday when my bike started acting up. It won't Rev up or has BAD! Throttle response. Like I'm only giving it quarter gas. I completely disassembled the carb and cleaned everything. Diaphragm is good. Air filter clean put new spark plug in and still the same issue. What could cause this?

 

Did you pull the line from the fuel pump to see if it has good fuel flow? Tank vent open and clear,same for the carb atmospheric vent? Plus water in the fuel can cause problems,but doesn't sound likely if problems started all at once.Old fashioned way to see if it's an electrical problem(if you're certain the carb,etc are in good order) is to hook up a timing light to the plug wire. If it flashes in time with the engine miss,then could be an electrical problem. Check simple things like a bare spot on the plug wire that can short to ground. Plus here's a section on these carbs on setting the float level properly on these BST40 carbs,plus this might help you in retracing your steps on the carb such as making sure the diaphram spring and needle components are assembled properly.The BST-40 Bible | Adventure Rider

 

I pulled the line from the fuel pump it has fuel coming out but not really a full stream.

 

Check that the vacuum line is ok,not kinked,plus you can pull the vacuum line from the carb and either suck on the line or use a mity vac to really put some pucker power to it. If flow is still weak,then pumps are too cheap to tear apart and mess with. Easier to replace them.Fuel Pump for Polaris Sportsman 400 500 600 Magnum 325 Outlaw 450 Predator ATV | eBay Wouldn't overlook testing with a timing light. If the light is continuous not intermittent with the engine limiting,then a partially stopped up pump may be the cause in not allowing enough fuel to get to the carb.

 

I pulled the vacuum line it has good vacuum. I tried running the tank line straight to the carb it started and idled fine but still had no power

 

IF you can say for certain that the carb,fuel supply isn't the problem,have the air box and filter hooked up,then it's possible it's an electrical problem. Best way on this is to use the trouble shooting guides in the manual along with the electrical checks.Just a process of elimination until you find the problem. 2002 Polaris Sportsman 500 Service Manual PDF Download I can give you a little head start on this. Black/red and green wires from the stator to the cdi should show around 440 ohms resistance. Pick up coil white and white/red should show around 97 ohms.

 

Was messing around with it today going down the road and I noticed it showed I was in reverse when in high

 

Then that's the cause of the limiting.. Check the connections on the gear position switches. One that controls reverse position will have a violet or purple wire. Possible the internal plastic lever has broken and shows stuck in reverse. This can cause limiting through the speedo.Plus both switches have been updated. Items #12,13.Dirt Cheap Yamaha, Polaris, Suzuki & Kawasaki OEM Parts & Accessories – Cycle Parts Warehouse

 

Changed the switches with working ones and still same issue

 

The limiter is inside the speedo head. If it's still showing reverse,then it's the limiter kicking in. Plus don't know if this reverse over ride bypass may help or not. May take a new speedo?

Pre 2003 and almost all models that do NOT have the combined override/Speedo function button.

Trace wires from the override button (gray/white & gray/orange) Cut the gray/orange and tape up both ends. Cut the gray/white and tape up the end which goes to the override button. Connect the other end of the gray/white to the red/white (ignition supplied 12v)