PM me you email address and I will scan the diagram for you, then at least you can see what youre doing, I havent looked at the problem with regard the correct diagram
The wrong diagram is in haynes ISBN 0 85696 661 4
The right diagram is in haynes ISBN 1 85010 300 3
This is the best one, cant understand how they got it so wrong in the other
http://cgi.ebay.com.sg/Yamaha-DT175MX-Haynes-Manual-DT125MX-DT175-DT125-DT100_W0QQitemZ150447971503QQcmdZViewItemQQssPageNameZRSS:B:SILF:SG:101
In the 'Wrong one'
They state the diagram is for DT175E and DT175MX...clearly it is for DT175E but not MX, look at the diagram, keyswitch is just two position and no parking lamp. Muddies the waters somewhat when youre trying to fix a lighting issue.