lost theeths on valves

[supermotard500]

Hy Guys,

when I bought my KX5 I found out, the motor didn't get a topend service since 1988.
So the carbon built-ups on the two drum valves forced them to seize in their bores and the steel teeths on the rack shear off the aluminum teeth on the drum valves. I didn't know that when I bought the bike.

3 teeths are gone from one valve, 4 from the other.  I will try to describe the former location from these teeths: When you look at the valves from down under (you see the short shaft and then the teeths) you see this shorter teeth. When you give him the number "1" and count further in left direction "against clockwise direction, the numbers 2,3 and 4 are gone from one valve, 7,8,9 and 10 from the other valve.

How many degrees the valves will turn "at work"? Is it possible to use the former right valve, 180? turned, in the left bore and the former left in right bore without lost of synchronisation at work?

Two pics, poor quality:

[supermotokx]

Hmmm

My bike is a '96, but the valves look pretty much like those on the pics. As far as I can recall (been a while since I've cleaned the valves   ) the two are not alike, which means they are right and left specifik. I don*t remember how much the valves turn from closed to full open but my guess would be 45-55 degrees - you can check it by pulling the valve operating rod (while holding valve alligened to the rod if it doesn't turn) from full open to closed. Remember to have the valve rod retaining screw in, otherwise you will pull the rod too far out.
 In any case I think you should get a new pair of valves  

Martin

[supermotard500]

as far is I know the main exhaust got a valve too after '88.

The two drum valves are similar, I already checked that.

If it's around 60? it would work, but I think it will be more so that the expansion chamber could be opened.

New valves would cost 100 Euros. If it's not working I would weld material on the broken spots and mill it to new teeths. But this would mean much work and the welding maybe bent the valves so that they should be turned on a lathe afterwards. That's why I try to prevent that scenario.