ORIGINAL: loughbd
I break in engines using the manufacturer's recommendation. They made it and I would think they know how to break one in.
Thats funny, because a lot of manufacturers tell you to run an ABC engine stupid rich for initial break in. And we all know what that does to an ABC engine. Don't we?
Manufacturers tell us to run our engines overly rich because that gaurantees that the connecting rod bushing won't seize on the crank pin. They could care less what that overly rich break in does to long term engine performance, they just want to avoid a warranty claim from a stuck rod bushing. It's strictly a C.Y.A. thing on the part of the manufacturers.
I haven't read an engine manual since my first new one that I bought over 8yrs ago. I read the manual on that engine and did the break in according to the manaul and I effectively ruined the engine. It was an OS 120 Surpass non-pumped engine, and I broke it in just like the manual said. Word for word. That engine turned into one of the biggest POS I have ever had the displeasure of owning. That was purely the fault of the break in. I didn't know it at the time. I thought 4-strokes just sucked. It wasn't untill I discovered RCU and started reading posts from guys like FBD and W8YE that it finally dawned on me why that OS Surpass was such a POS. It was because I broke it in according to the manual. Who better than to tell you how to break it in but that manufacturer--right?
Total BS.
Didn't take me but one engine, and $350 to figure out what was going on.
My break in procedure NOW:
I add 4oz of castor to a fresh gallon of 5% Omega fuel and break them in like I plan to run them. WFO and screaming bloody murder with a small diameter--high pitch prop that will let them run at MAX rated RPM or darn close to it for a couple tanks. Haven't cooked one yet, or had a turd engine from my break in procedure in the last 8yrs.
Break it in like your trying to break it. If it breaks, then send it back. If it doesn't break, then it never will. Babying an engine with too much fuel and low RPM isn't really babying it at all. It's ruining it. They are made to run, and run well. Start it up and run it WFO with the main needle about 1/2--3/4 turn rich with a tiny prop and let it scream.