I have a 2000 sportsman 500 and after riding it for a while it will start to miss usually under load like climbing hills. I have tried new gas I have changed all the fluids but with no help. If you shut it off and let it sit for a while it will start up and run fine for a while and then start doing the same thing. I need some help trying to figure this out. Is there anybody that can help.

 

I would try some cosmetic stuff first. These machines are sensative and it could be something small. I would find the fuel filter and replace it. Clean air filter. Check the precleaner. It would't hurt to crank it up and spay some carb cleaner in the intake. Change the plug too. Go ahead and clean out the spark arestor.

 

That covers the areas I was thinking of. I'm not going to say anything stupid, like when I heard someone tell a mechanic the engine was missing, and the mechanic asked him where it went.

 

Check that the gas line to the carb is not close to the exhaust, they will vapor lock if the fuel gets hot.

 

I had the same issue and the center lobe on the cam shaft was completly worn. Thus not allowing it to remove exhaust properly and crawling like a snail. This is a common issue with the 2000 after speaking to my local dealer. I replaced it as well as the rocker arm and she runs like a champ!

 

i hhad the same thing on my scrambler 500 it has a sportsman engine and carb in it. under alot of load running hard oil comes out the oul over flow. then it gets a lil in the filter and chokes it and spitts sputters and if it is bad enogh it will even stall but it will mostly just spit bogg and not go anywere. but if i took teh filter off it ran fine. i have no clue y the oil over flow goes strait into the air box lol it is 2 lil holes at the front or the air box on the scrambler.

 

Missing under load is a tell tale sign of ignition break down. I would look at the ignition components. Plug,wire,cdi/coil. In general a faulty ignition component is more likely to show itself when hot as heat tends to increase resistance.

 

yea hot and under load is differnet the spark doesn't know what is under load how would it lol the fuel does whenit gets held up it needs more air and fuel to make more power and if teh carb isn't working just right it will bog eather clogged jets fuel filter or air filter or wet air filter from oil because it won't get more air and fuel in to make the power the spark if it works when its hot not under load then it will work under load.

 

Not true, higher load increases cylinder pressure, which in turn increases electrical resistance in the fuel/air mixture.....internal combustion engine 101.

 

Check vent line to fuel tank while you're at it. Not that this will cause the engine to miss, but....