maybe a bad valve
 

my brother has a 2002 scrambler 500 and it has many many miles on it over 10,000 for shore and ive never ever touched the motor at all but i noticed today there is a weird sound coming from around the valves when you give it over half throttle im not shore if it would be a bad valve or maybe they just need adjusting i cant hear it going slow or at at idle is there any way to tell if he has a bad valve without tearing into the motor?

First I would check the valve clearance .(006 intake and exhaust) If valves are with in tolerance could be worn cam chain noise especially if it really has around 10,000 MILES (Guessing on mileage I assume!!) Plus noises can radiate towards the the top of the engine from other engine areas or even from the clutch areas also! Plus does it run ok OR have any other problem other than the noise?? OPT

just put 2 brand new clutches on his bike he had a epi clutch kit i put the purple spring and he's weights in the primary clutch and we bot a brand new after market helix for his secondary so im shore thats not what it is. And it really dose have over 10,000 miles on it. I have the feeler gauges could it be the valves need adjusting how often should it be done ive never touched it.

By the book EVERY 100 hours or a thousand miles. OPT

geez! :/ 1000 miles so im hoping thats what it is i really dont want to open up that motor i just got done doing a 2002 sportsman 700 and if its anything like that im just not up for it.....but just letting you know i had a head unit with 9000 miles on it and i put a new one in it and i have not even looked how many he has put on it but i bet its a lot the 500s are really tuff motors.

Just remove valve cover,remove square plate on head on the right side,pull recoil slowly and as intake valves go down and start to come up,look at cam sprocket index pin(where sprocket aligns with the cam) and when the index pin is STRAIGHT UP in CENTER of head this is TDC. Then you can check/adjust valves. Plus you can check if cam chain is very loose,should be fairly tight. OPT

i will check they must be off and i will check the chain as well.

i'm guessing chain as well, but if the valves have never been touched in that amount of miles then either or could be.

ok so i tore into the valve cover to find they did not even need adjusting i took the clutch off and revved it up i can still hear it the chain has no slack in it but im not really shore how to tell if its worn it seems fine. I have a 2002 sportsman 400 would the valves be the same im assuming the cams are not the same but could i just take the head off the 400 and put the cam from the 500 into it the 400 only has 3000 miles on it due to a bad head gasket.

they are the same part number so they should interchange.