Motorboy

Hi all folks!

I has overhauled my G-Mark Twin .30, replaced the two pistons and now the engine has very good compression as a new engine. I replaced these pistons cause there was 0.5 mm ( 0.019 inc. ) deep spot of rust in surface at these sleeves. Removed rust when i lapped the sleeves and maked new pistons adapted to the sleeve.

The cause are the early owner replaced the fuel with castoroil to fuel with Aerosynth, then the engine was worned out + spot of rust in sleeve surface.

The sleeve are of steel and piston of cast iron.

Here in Bergen city in Norway are not easy to buy the fuel with pure 20% castoroil + 10% nitro.

Today i saw the Omega Aero 10% in the hobbyshop and this fuelcan has 17% oil who are blended of 30/70 castoroil/syntetics oil.

And i am in doubt about i can use the Omega Aero fuel without worn out/damage the pistons/sleeves when i want to break-in the engine + use the Omega fuel allways for this G-Mark .30 Twin.

I am proud to be owner of the G-Mark Twin engine after i got the engine of early owner.

Jens Eirik

Jim Thomerson

I think I would add castor to get it up to about 22-23% oil. I'm not sure, but I think Omega fuel % is by weight and not volume. Anyway, a little extra castor couldn't hurt on break in.

downunder

With an engine like that I'd be tempted to treat it like a Fox 35 and use up to 30% oil with most (if not all) castor. The rule of thumb for cast iron pistons is 25% all castor but I doubt that a blend would hurt. I'd run it in with very high oil content then maybe drop to 25% and see what affect that had on the head temp.

Fuelman

My Feedback: (6)

Motorboy,
Use the 10% Omega and add some castor oil to it like downunder suggests for this application.

Motorboy

Thanks, i shall buy fuel and add more castoroil..

Jens Eirik