Powervalve Problems Part II

[Liono]

A follow up to this thread which I started recently:
https://www.bikechatforums.com/viewtopic.php?t=38179

I was having a play around trying to de-restrict my Yamaha TDR125 by fully opening the Powervalve, and this seems to cause some problems with the running of the bike. I have actually changed it back to the restricted settings so that it works properly, but would like to try opening the Powervalve again in the near future.

Basically, what happened when I had turned the valve was that the engine cut out completely after about 5 minutes of riding. As a result of the advice on the other thread I changed the plug, which was black and fairly oily. A search reveals this page:
https://freespace.virgin.net/steven.crook-dawkins/tuning%20guide/sparkplugs.htm
which suggests that the mix is too rich, however I hadn't looked at the plug before I made the changes, so it could have been like this anyway. I guess what I'm asking is; should I wish to de-restrict the bike again, how do I know what changes i need to make so that the engine runs properly? Through searches I've found how to change the idle speed and mixture, but how do I actually know which to change and by how much?

[Smoto Bob]

[simon1221]

you got a haynes manual? may be pretty useful to get one

im thinking that if you derestrict it you may have to change the settings anyway
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DNA50 (sorry) ->> TZR125l >> GPZ500S