Hi guys, for your records below is the official answer I got from the factory concerning conrod life for the Sirio S12. Also I did measurement to crank pin on a new stock engine and found that it has 4.428mm.

"The right play between crank pin and conrod bushing is 0,04 - 0,05 mm. I don't know if you're able to check it, but I suggest you change the conrod every 2-3 hours running.
The life of the conrod depends mainly on the fuel you use, as the lubrification and the right carburetion keeps your engine running well for long time."

Regards,

ANDREA ROSSI
Lavorazioni Meccaniche srl
Via Meucci, 3 Seggiano di Pioltello Mi Italy
Tel +39 0292160235 Fax +39 0292160581
Visit our Web Site at :
WWW.STAR-MOTOR.COM

From calculations about conrod life, according to Sirio factory, one should change the conrod between 0.4756 to 0.7133 gallon.

How come??? Well, if a 75cc tank lasts an average of 5 minutes, one makes 12 tanks in 1 hour, which is 900cc. So according to Sirio that says change conrod after 2 to 3 hours running, that means change conrod between 1800cc and 2700cc of fuel. Now if 1 gallon has 3,785cc, that means the lifetime of the conrod is less than one gallon.

BREAK-IN

After reading a post by Andrea Rossi in the Sirio's web site, this is the correct Break-In procedure for the S12's

1.- One (1) tank in the bench at WOT with very rich setting of HSN, avoiding it to go on 4 stroke.
COOL DOWN
2.- Three (3) tanks on the track with very rich setting of HSN, and tuning the HSN at the end of third tank to get almost full power.
COOL DOWN
He says after that, the engine will give more power after every new tank.
3.- For 20% Nitro, use .20 head shim and N° 7 Glow plug.

Which means that Break-In should be done with more or less 300 to 500cc of fuel.

AFM