How can an airbox get too much air? If the air filter is on properly and the clamp is tight, mine runs just fine with the air box lid off. Seems like it would only run bad if it is not getting enough air. The more air the better right (as long as the engine is sucking the air through the filter) Can the engine get too much air if it still going through the filter and there are no leaks in the connections or the carb?

 

I don't know enough about the subject to be an expert by any stretch of the imagination. There are several excellent guides online and in hardcopy discussing the subject. I've read a few of them, enough to be dangerous.

I know it sounds like the more air the better but it doesn't always work that way. If the carb is allowed to suck in more air that it can provide fuel, it will lean out and sputter off idle and possibly backfire. The unrestricted intake of air changes the fuel/air mixture and causes the motor to run lean. 2 strokes and 4 strokes react differently. Changing the restriction of air inflow (or lack therof) on a 4 stroke can adversely affect the performance. Try taking the airbox lid off a sp500 4 stroke and it will idle fine. Gas it for a second and it will seem alright. Hold the throttle and it will rev up a bit and then bog down with a blah sound.

 

I dont know if the Ranger has the ETC on it, but that can cause the same symptoms on a 500 Sportsman if it is out of adjustment. Worth a look. Good luck.

Ken

 

My Scrammy had a similar prob. Turned out to be a crimped vent tube on the fuel tank. Go figure , not enough air.

 

I would start by checking the camshaft, if your oil is/was dirty or full of moisture the exhaust lobe on the camshaft seems to be the weakest link in the system and it esay to pull the rocker cover off on a Ranger. Some of the early Rangers did have a problem with the intake manifold screws falling out but they still revved up. An easy check for the cam is cover the air box opening with your hand, if it seems to pulsate the cams out as the exhaust is being forced out the intake.

 

My '02 Scrambler 500 4x4 acted very similar, spitting and sputtering when I got on it but it would idle fine. What I did sounds really simple but it worked for me so I'm offering up the suggestion. I cleaned the air filter and spark plug. After that it ran great.