Hi Auke,

Hmmm. The Swiss jetting/carburator is probably mainly based on higher altitude = less oxigen in the air so basicly smaller jets. Is that right?

If I remember right: the main jet only controles the mixture from half to full throttle. the needle controles it from 0 to 3/4 throttle, the idle jet when throttle is closed. Off course these controles overlap.

As far as I know the right procedure to 'read the plug' ('Coffee with milk' should be what you want) is the following:
To check if the main jet is correct: ride full throttle, if possibly up-slope or with head-wind, for a while and than cut the engine with the righthand switch (and use the clutch off course). Then check the plug (after you stopped :-)
Do the same with half throttle to check the needle position.
When you check the plug after the engine has idled you probably only check the idle adjustment. Which in your case could explain that indeed you cant adjust it right. The screw fully in and still not right probably means it gets still to much air ---> white plug.

So I wouldn't change the main jet until you are sure it to lean at full throttle.
Make sure the needle position is original 1VJ (needle up = clip down... can be confusing in the manual)
If it is try to lower the needle one position en check if you can get it idle properly. If not you may have to change the idle jet for a smaller one.

I'm not sure what you mean bij 'headers' but probaly the original (1VJ) size gives the least chances on problems.

Peter

__________________
Peter Kik
Zaandam, Holland
peter.kik@tip.nl