Jake, it's me, the guy who spoke with you a length about the Arrow engines on the phone last year. Mine seized, and I was looking for parts.
You have a Hirth, so you need to connect to
http://www.recpower.com
They are in Ohio. Matt is the main guy I think, he is very knowledgeable and helpful.
I downloaded a manual for my Hirth 2706 at the Ultralight Store. The 2706 is a 625cc, 62 hp forerunner to your 2703 I think. If you want, PM me and I will send you a copy to your email.
When breaking in a any new motor I recommend never leaving it at the same power setting for more than a few minutes at a time. The idea in break in is to heat cycle the motor completely, each time increasing load and RPM, and endurance of that. This will make the bearings, wrist pins and rings happy little campers.
For the first 10-15 minutes the motor should not get above a SMOOTH idle speed, while any burrs and foreign dirt or debris is eliminated from the moving parts. Once that crap finds its way to the bottom of the crankcase, it will then eventually be blown into the top end for combustion and elimination like a turd out the back door. This should settle the bearings, and break the surface of the rings. Shut it down and let it cool for an hour.
The next break in period is primarily for the bearings and RINGS, the latter being SUPER CRITICAL. You only get one chance to properly seat the rings, and if you blow it, you'll get blow-by, and that will definitely lead to a seized 2-cycle motor. Some motors have been improperly broken in, rings have not been seated well, blow-by occurs and at some point this leads to a confusing engine failure. On a 4-stroke, the break in is different, as you must properly polish the cam surfaces at high temps so you don't wipe them at +redline later. The point is this: KEEP ENGINE RPM TO A MINIMUM UNTIL THE ENGINE HAS COMPLETELY HEATED UP EVENLY, THROUGHOUT. RUN THE MOTOR AT OPERATING TEMPS THROUGH THE LOW END OF THE POWER BAND, WITH LIGHT LOADS. On your 2-cycle gyro, you can taxi around the airport for 20-30 minutes, after your first idling break-in, and temps have increased suffuciently. This should seat the rings at low loads, and should help prevent wearing too much material from them initially while they are still "soft".
Bring it back to the shed and shut her down. Leave her alone and go have lunch. When you come back, you are ready to have another go. This time, warm it up like you would any motor, taxi it around for 15 minutes, then take to the runway. Do a bunch of crow hops. Now you've heated everything up to temps, and run everything in at full load, but only briefly. This should cycle and flex the motor properly, while not leaving it at full throttle long enough to stretch the rods too much too soon, and allow the cases to move around the crankshaft a bit to respond and recoil to their load. This should prevent removing too much material from the surfaces of the rings, and prevent future blow-by. The rings have completely seated by now, and the surfaces are now so hard that they should not continue to lose metal too fast, provided you don't try to run a cold engine too fast.
Bring her back to the shed, and leave her alone until she cools completely once again.
On the fourth and final run-in, take to the air for a few laps around the airport pattern. Play with the throttle, do not leave it at any one speed too long, you do not want your motor to settle in to a "sweet spot". (If this were a race car, I would say shift below redline on every shift for 3 laps, then hit redline on every shift for 2 laps, then go 200 rpms over redline for 1 lap. Run a cool-down lap or two, then bring it back to the pit.) Bring your bird back to the shed for inspection.
Of course, in the intermediate of all steps, a thorough ground inspection should be conducted, checking for loose fixtures, plugs, connections, nuts, bolts, fuel lines, etc.
Now I would say, after all this, you are ready for "routine" flying without leaving the pattern. After 20 hours, you should be good to go anywhere you please.
Happy gyrocoptering! May your motor give you many, many, trouble-free hours of satisfying performance.
