Phil, I've made it a habit to always run FAI fuel to begin with in my Stalkers. After flying and trimming out the plane, I can then experiment with adding small amounts of nitro. Virtually all my Stalkers are running fine for me on FAI fuel.

 ..and remember that FAI-fuel has only castor as oil. Differend synthetic behave in differend ways and some can cause weird problems in high-compression/tight fit engines on East-European style engines (sqeek, detonation..). I use 15% castor and 5% Motul Micro synthetic in my Retro's, it seems to work and engine stays a lot cleaner than with all castor. L

Not exactly true, Lauri. It depends on what event the "FAI Fuel" is specified for. Because of this, over here, any glow fuel without nitromethane is referred to as "FAI Fuel". On the container, verbally, and justifiably, per the section below, as copied and pasted from the online rules for the F1C event.  Steve
 
"Rule B.3.1.a. of Section 4b does not apply to class F1C. Fuel to a standard formula for glow plug and spark ignition motors will be supplied by the organisers, and must be used for every official flight. The composition shall be as follows: 80% methanol, 20% castor or synthetic oil."

It is quite impossible for me to get FAI fuel (except by expensive mail-shipment)  Our local hobby shop sells SIG, so I use 10% nitro with combination oils in my Stalker.  Added a head gasket, per instructions.  The  Stalker on-line instructions indicate that "some" nitro is just fine for Stalkers-- (they don't blow up, or anything like that!)

Floyd

I'm not sure that FAI fuel is specifically all castor lube. My experience runs differently.

The online instructions for Stalkers specifically warn agianst using all castor with their engines, citing the need to de-coke the engine to remove the deposits castor leaves behind.

The metalurgy used is such that high castor lube is not needed to protect the engine. These are not iron piston/steel liner engines like a Fox, that require high castor lube, In fact, the instructions say that they prefer all synthetic, but if you must run castor to limit the amount. I personally run a blend, using 5% of the total lube being castor. It has worked very well for me, with several engines running 6 or more seasons with no problems.

Of course, one can run any fuel/lube combination they want. The worse that will happen with all castor is that the top of the piston, and cylinder head will get covered in burnt on castor and lose power until it is taken apart and cleaned. One of my clubmates experienced this first hand with a Discovery Retro he was running. The power and run difference was very noticable after cleaning.

Hi all, mines run perfect with 20% Klotz, 2% Castor (you know...protection, etc..) and 5% Nitro, same numbers as a good Tigre 46 (tested with mines).

Regards.