I have a 99 magnum 500, when I rev it up past half throttle it bogs out and pops out of the air filter. I tried a new carb but it still did it. Someone told me it could be a loose valve or the timing. Anyone have any suggestions?

 

The exhaust lobe on the cam may be worn so the exhaust valve doesn't open properly, The popping noise is from the exhaust pressure going into the intake when the intake valve opens.

 

Can that be fixed or do I have to replace the whole cam?

 

The cam would need to be replaced, pull the valve cover off and watch the valves open as you rotate the engine over. They should both move the same amount visually, also look at the cam lobes-they should look the same (intake vs, exhaust)

 

Mine is doing the same thing, but i have a 00' Sportsman, same difference. It was running ok and we were just easing around mainly on some back roads. I noticed that it sounded like it was having some detonation, but it was a hot day, so I just didn't run it too hard. We went around the top of the mountain and coming down the other side I noticed that it didn't have it's usual ammount of power while going through a mud hole. On the way back to the truck, we were cruising easily again and I was having to give it more and more throttle to maintain speed. Before I loaded it in my truck it probly couldn't do over 20 miles per hour. So I put in it's first ever new spark plug the next day, didn't help. Adjusted the valves, the intake was a little tight, and the exhaust was a little loose, but it didn't strike me as a problem. Pulled off the carb and cleaned it really good, although it wasn't dirty in the first place, didn't help. Went through as much of the wiring as I was willing to do tonight, and she still won't take throttle over about 20%. If you just hold it wide open it bogs at approximately 3000 RPM and will pop through the carb every now and then. Checked timing (as good as I could) for the cam and ignition, and they seemed alright. But when I did a compression test, it only made about 80 lbs. It starts fine though, and smokes extremely little if you really get it reved out and let off it, or hold it with the brakes for a few seconds while in gear. I also pulled off the silencer and checked it and all the fuel lines for sufficient flow. So I guess it sounds like a cam for me too, right? It seems like I heard about this happening a long time ago to other Polaris bikes. Well it has had a pretty rough life so far, and never let me down untill now. (I have owned it since it was new, and take care of it, but really have shown it no mercy) Thanks if anyone read this book I just wrote on here, but I'm done. Cam???? U think??

 

Has anyone got there problem fixed???? Going thruogh the same problem's please HELP!!!!

 

I have had the same thing happen to me because of a cracked insulator on the plug. Start with the cheapest/easiest things first and work your way up.

 

Buddy's 98 SP 500 had an exhaust cam lobe that was completely gone. New cam, problem solved.

 

Hammer,

If you have that same problem on your 700, then check the carb boot that runs from the carb to the engine, they are notorious for splitting.

 

"04' twins were notorious for that boot splitting problem. I have not seen much since.