Can anyone tell me what the compression spec is for a 03 polaris sportsman 400. I'm only getting about 100psi on my gauge. Engine will not start or run off of either.

 

About as high as you can get on the 400. Same thing on the 500 as the cam has a compression release device that opens the exhaust valves slightly so it can crank a little easier. Manual shows between 55-90 psi on average,some can get a little more.Start at the basics,check that battery connections are ok,has spark,fuel to the carb and a good clean air filter. Manual can help you pinpoint most problems.Just use the trouble shooting guides in each section. If you still have problems then just post what you've found and hopefully can get some help.Here's one for 5 bucks.2003 Polaris Sportsman 400 Service Manual PDF Download

 

I have installed new stator cause it lost its spark. I have spark now. The fuel system is new. New carb and pump. New sparkplug and coil. Checked the cam lobe for wear and it is good. Valve are working correctly. I can get it to start sometimes but it won't rev up and then it backfires through the carb and shuts off

 

Did you check the new carbs jetting,is the same as yours?Check that the spring and slide are ok? Opened fuel bowl in carb to see if it's getting fuel? Pull the black kill wire from the cdi and see if it keeps running ok.If it does could be an a intermittent wiring short in either ignition on left control switch kill circuit or a cdi problem itself. Check that the face of the pulse coil has between 0.16-0.40 clearance between it and the flywheel tab.If compression is that good(100 psi),valves are set at .006 intake and exhaust,I'd kinda rule out a mechanical problem from what you've mentioned. Could even be a coil breaking down or plug wire break that could be intermittently shorting to ground.If it won't crank on ether,somethings wrong if you have compression,fuel, spark? and air.Wiring schematic along with trouble shooting guides for electrical and mechanical problems from the manual are still your best bet rather than someone just guessing what the problem may be. The 5 buck manual can be worth it's weight in gold in situations like this. Even clutch problems can cause an atv not to rev up if ramp buttons are worn.

 

OK. I really appreciate the help. The bad thing is that I don't know the history of the bike. My dad bought it from a guy he works with and it was in his garage when he bought his house. So I started messing with it to see of it was worth getting running. I will refer to the Manual and check the rest of the system. Thanks

 

Removed the carb and found the jet was smaller than the old carb. Swapped the jets and installed another new plug. It now fires up with the throttle cracked about a 1/8 inch but doesn't rev up. It Biggs really bad and when it returns to idle it shuts off. I've tried it with the filter on it and off it. The only thing I haven't replaced is the cdi.

 

Adjust the throttle cable to where you only have 1/8" slack at the thumb lever at idle or the etc switch contacts can touch and kill the engine. If this doesn't help,just get the manual rather than throwing parts at it!
Plus here's a section from the manual on carbs and adjustments to help eliminate a carb problem.https://www.google.com/url?sa=t&rct=...,d.aWw&cad=rja

 

OK I have adjusted the throttle were the contacts are now open. I can only get engine to idle and doesn't rev up. I've tried it with and without the air filter box. I've heard something about crank seals causing lean conditions.

 

Has to have the air box and filter or it will run crappy,won't take throttle.Only remember a couple 500s that had crank seal problems.Both were the one behind the drive clutch and would still run but slung oil all over.If it happened on a 2 stroke it wouldn't run at all. Only things I can think of it's still a carb problem somewhere,check that it's getting fuel by pulling the carb line and cranking the engine over.Should be a stream of fuel.Or you might recheck that cam even though you say it's a 2003 model.The manual still has good trouble shooting guides in each chapter on mechanical,fuel,carburetion,electrical,etc that you may have over looked.