Originally posted by BrainTeased
Is the dark piston surface a bad sign? i remember with my VoneS engine after 3-4 litres the top surface of the piston was still gold and looking like brand new!!! now with my MR-12 it went dark within 1 litre or so... but i have changed fuels from a 15% nitro 18% lube oils (voneS) to 16% nitro and i think 10% or so lube oil (MTX-3 mr-12)
No it is not, actualy it is shows that your engine is running in it's best performance-temperature etc.
It should be realy shiny dark. If it is not shiny-it means the fuel blend you use isn't the best fuel.
This is one of the way I am checking cobustion chambers on my engines. After 3-4 tanks of fuel at racing tunning, I can see on piston how my ports are working and what correction has to be done for best performance.
If the is no warnish bilt up ( shiny surface), I will recomend do not polish it. Only if you see real build up, then you can try to remove it by corse piece of fabric. And do it on flat surface.