Hi there,

I recently bought a NovaRoss .12 engine and finished run in with about half gallon on it. When I disassembly the engine for maintenance, I found that there is a coat of black, tar like, stuff stick on the top of the pistol surface. I tried to use motor spray to rub it but couldn’t clean it off. Does anyone here has an idea about how can I remove it or it is normal to have it on the piston.

Thanks

PS.. Im using Blue Thunder 20% fuel...

Tooth paste or dentifrice and toilet paper is your good friends. You will need it everyday....

You must be useing a fuel with a lot of castor oil! Castor oil is very sticky, I use rocket science fuel and after 1/2 a gallon the piston will wipe clean with my finger.

Normaly if your piston s white clean-it means it didn't work yet. Even after 2-3 tanks of work on racing tuning, it should became dark brown and later black. It doesn't supose to collect varnish and if it is, as Slotmachine mentioned-that fuel isn't the best. Try to use some very well blemded as O'Donnell, Bayron. I have very good expirience with them. Also, you can contact to Stefan and if you live in his area, he is blending very good fuel, I recomend it to you.

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.

thanks for the great tip!!! im pretty sure mine was like half shiny lol how shiny does it have to be? maybe i needed more light in it? i run the fuel brand "hot stuff" 16% im not sure if america has heard of this brand.

Thanks guys for yours' great comments.