03 300 exc top end noise

[SmokinRZ]

My friend has a 03 300 exc hat has suddenly started making top end noise like it is worn out. He is a Sr rider with only 4 or 5 enduros on the bike. It seems like it started all of a sudden yesterday in an enduro. Bike is well maintained with clean air filter and good 2 stroke oil. It is hard to believe the top end could be shot this quick! No knocking or anything, just sounds the top end of a ratty old 93 insterad of a 03. Thanks for all replies!

 

[KDXfile]

Check and see if the pipe is loose or rattling against something. You should get a year or two out of that top end.

 

[wsmc831]

my 02 has been trouble free for almost a year, with about 10 enduros on it. i've read 2 or 3 years is a normal interval for top ends on them...so I really doubt its a serious problem.

 

[kev_rm]

my buddies 03 EXC lost it's top end at 10 hours because of a cylinder plating flaw which ultimately resulted in a sieze and a cracked port. Might be worth the price of a gasket set to do a tear down.

 

[KTM Mike]

Does the noise change (quite down) when the clutch lever is pulled in? If so it likely is clutch rattle from some wear on the clutch basket. My 97 did it bad - so does my 2000. I bought my 2000 with about 800 miles of riding on it - and it did it even at that point (it now has 3000 plus) - its never been a problem, though eventually I may have to replace a clutch basket. Two of my riding buddies have 03 250excs - they both do it , not quite as much as my bike though.

 

[ktmrandy]

It is possible the power valve adjustment has changed or come loose and is allowing the piston to hit the valve. Pull the spark plug then turn the engine over and make sure it turns over smoothly. Pull the side covers off the ends of the power valve and verify all screws are snug.