Combines rotor out of balance

possibly crud inside roter had mine balenced at welding shop in auburn ontario they cut it open and removed a lot of crap from inside

Sounds like dirt_dust inside the rotor. Inspect the rotor front to back and look for any holes or cracks at seams and rasp bar mount pads. Also stone damage dents as well, any thing that could let dirt go inside the rotor.

Thats 3 for 3 on dirt inside the rotor. Try spinning the rotor by hand. If the heavy spot changes its definately crud in the rotor. Good luck

Had a 1680 that got out of balance and it had a lot of chaff in rotor and there was no holes or dents in it. It did have a 2000 hrs on it. I cut a 3 inch hole in it with hole saw and used a shop vac to clean it all out. Then used the same piece and wire welded it back in. End of rotor shaking.

Before you start cutting holes, just for the sake of diagnosis, take a long bar and stick it through the grates and lift on the rotor toward the rear. If it moves up and down, it may be the drive hub. If not, at least you know for sure first.

Well I think I found the problem, there was a dent on the front cone behind one of the elephant ears, someone has had a stone through, I think the dent has put it out of balance, anyway spent 3 hrs re balancing it properly, so we shall see how we go. I think there is very little dirt inside as I can't hear anything. Thanks for the info!

The only method for removing material from inside a rotor is to open it up between all internal bulkheads and this allows inspection of the bulkheads to check for collapsed areas. It may also be necessary to reskin at least a portion of the rotor. Acetylene torch is OK, but if you do this, make sure your face is away from the initial piercing cut -- the rotor won't explode, but the dust may burn and you might see some blowback.

put a bar under the back of the rotor and see if it moves up and down,if so bushes could be worn out on hub.causing vibration,i spent hours trying to balance our rotor without success until checking bushes for play,replaced and solved everything