Chop Test Results

[2T5]

how does it pull wide open power wise? if its too rich it will lay down and get boggy. if its too lean will cut out.

theres a point where it can be -too- rich and 'wash' the plug clean because you cant burn all the fuel.

Under hard acceleration it pulls really hard but does seem to struggle to rev right out. It no longer splutters, it's just a bit sluggish. It doesn't want to go to the top speeds that I have previously seen so you might be on to something there.

[teazer]

Keihin jet number are typically a measure of the diameter of the orifice.  Mikuni large Hex jets are flow measured. So if you go for say a 100 to 200 in Mikuni it means twice the fuel but in a Keihin it means 4x the amount of fuel.
A 200 Keihin is about a 400-440 in a large hex mikuni. 

Next thing to think about is that C10 IIRC is a slow burning fuel as witnessed by it low RVP, and tends to feel less responsive to throttle.  The most responsive fuel I ever tested was U4.4.

Next thing to keep in mind is that in the US, most race fuel is leaded, and most of the data on reading spark plugs relates to leaded fuel. In Australia, IIRC leaded fuel is banned even for racing.  We used to run a TZ on 100 AVGAS which used to be legal. Not sure what the current regulations are. C10 requires a slightly richer mixture than street petrol, so with those variables, it is a test it and see situation.

The plug looks like it is running cooler that expected, which suggests that it could use a touch more advance and perhaps going down one jet size or maybe 2. OR leave the C10 at home and try whatever fuel you ran it on before and jet for that.