03 crf450 top end rattle

[Timmay#678]

My cousin got himself an 03 crf450, and had it completely rebuilt, with new bottem end, piston, timing chain, valves, springs. He used it for a few hours, until a bad rattle came in the top end, he stopped it straight away, and has given it to me to have a look at.

The rattle seems to be coming from the top end alright, I took off the rocker cover, and nothing out of the ordinary there, timing chain still tensioned nicely, automatic decompressor grand, and all the valves clearance are within spec, including the decompressor arm. I checked the timing next, it seems to be very slightly off, but not enough to jump a tooth in the timing.

Does anyone have any more ideas as to what it could be in the top end, before I pull off the head, and check if the valves are hitting the piston.

 

[truckster225]

This may sound dumb, but is the exhaust rubbing anywhere? Also, the same thing happened on my Suzuki, I could NOT figure it out! Turns out, the gas tank bolts had come loose under the seat and THAT was making the sound.