The only ways I can think of to get 4 bent valve stems is for either some one to install a cam chain with improper positioning of the cam relative to piston TDC, and them try to start the engine by pulling the bike with another vehicle.
If so you probably have more than just valves to replace and $1000 may be a low number.
The other thing that came to mind was for the cam chain to break at full speed. You would most likely notice a hole in the cam cover if this happened.
Its more than likely a broken valve spring. If the valve hasn't dropped into the cylinder then the fix is much cheaper, even if the valve is slightly bent.
I dropped a valve on my 501 because the valve spring broke. I removed the head and had the head reworked then reinstalled it myself.
The valve guide had to be replaced because it was damaged also.
Total cost for the head work was $265 US, this included a new intake valve and intake guide, and a valve grind job on the head.
Separately I had to buy 4 new valve springs.
If you are not mechanically inclined to do the easy work you should get another estimate. Some minor disassembly is necessary to determine the failure mode and give you a good estimate!
The minimum would to be to remove the valve adjustment covers for a look see.
Regards,
Joe
