this 600 red head runs odd at a steady rpms of 4500 . was backfireing . now kinda pops some under 5k . carbs are clean . tors by pass , no diff , reeds look good . temp light come on some times , dies compleatly some times , then starts right up and goes 
YamahaSXR700
Member
check your plugs my buddy had put some br9es in it andit was back firring put some br9esya
well it works they had put in 2 b9es in it now with 3 br9eya plugs its good to go
mountainrider
New member
My 1998 600 xt was acting this way, found out it was a crankseal. Check for air leaks.
redrider24940
New member
Not to step on your thread, I have the same problem on a 700 sx. I can only get like 70 MPH out of it. New plugs & clean carbs. Could it be the Coils?