I take it that it must be a lapped engine.  If so, mount it on the bench with a good mounting system.  Start it up and run first time just on the rich side to get it cleaned out if you haven't cleaned it out already.  We were surprised to see how much crud is inside a new engine when we first started looking inside before starting them.  You only need a couple of minutes on it, then take needle in a little and let it run for at least 2 minutes.  Shut it down and let it cool out.  That is you should feel no heat anywhere on the engine, especially the bottom end.  Start it up again and let it run again for at least 2 minutes to get it thoroughly warmed up again.  If you have a tach, it is better as you can check to see if you can reach the rpm you want to run at.  Another little secret is run a prop that is 1 inch less in diameter than you plan on running.  After about 20 cycles of this then put it in the plane and fly with it just on the rich side.  If it is a ringed engine, I usually run on bench to get a needle setting for a couple of runs and put in plane and fly.  Make sure you have good fuel.  My Brodak 25 had one run on the ground and was put in the air.  I am doing full pattern now after only 6 flights on the plane.  Have fun,  DOC Holliday

Steve,

If it is a new G.51, you should have the manufacturer's instructions in the big red box. Sure, they will go on and on forever about the R/C version, but the same principles apply. Yours is almost certainly a ringed piston, so the time and load recommendations shouldn't be much different whether there is a carb or a simple venturii mounted. Fuel and prop recommendations should also serve well.

Luck! , and there is a lot of reference discussion for this engine - worth a little digging, starting with the thread RandyS suggests.

I take it that it must be a lapped engine.  If so, mount it on the bench with a good mounting system.  Start it up and run first time just on the rich side to get it cleaned out if you haven't cleaned it out already.  We were surprised to see how much crud is inside a new engine when we first started looking inside before starting them.  You only need a couple of minutes on it, then take needle in a little and let it run for at least 2 minutes.  Shut it down and let it cool out.  That is you should feel no heat anywhere on the engine, especially the bottom end.  Start it up again and let it run again for at least 2 minutes to get it thoroughly warmed up again.  If you have a tach, it is better as you can check to see if you can reach the rpm you want to run at.  Another little secret is run a prop that is 1 inch less in diameter than you plan on running.  After about 20 cycles of this then put it in the plane and fly with it just on the rich side.  If it is a ringed engine, I usually run on bench to get a needle setting for a couple of runs and put in plane and fly.  Make sure you have good fuel.  My Brodak 25 had one run on the ground and was put in the air.  I am doing full pattern now after only 6 flights on the plane.  Have fun,  DOC Holliday

 Thats's great Doc{re; the Brodak}..I was jittery about paying 100 bucks and not doing it right. I believe Dee Rice did the exact breakin you did. I ran a qt. thru it on 2 min intervals with cooldowns..and, on the last run, turned it verticle, and it made an instant break. That is one super engine in my humble, 35 year retread opinion. Take care, Bob

Well guys i ran the S.T. today with O.K. results First i had trouble getting it to keep running after removing the glow starter. At  one point the glow starter popped off the glow plug, hit the prop and broke in two! Other then that no damage was done  . So far it's only go about 6oz through it but it is looking good so far.


     Thanks everyone for the advice.
                            -Steve