I bought a GMS .47 to replace the old OS .40 my dad got for me with my trainer; My old engine was used so I never had to break it in. I decided to go ahead and break in my new GMS today which was probably a bad idea but it was too tempting and I just couldn’t leave the engine in the box. Here's what I did. I ran the first tank at full throttle really rich then leaned it out and ran it at different speeds with the second tank. It seemed to run alright but now when I turn it over and it reaches tdc it kinda sounds like the crankshaft is binding with something. I duno if this is normal and it just takes a while to get everything broken in, or I did something wrong and screwed it up. If anyone could offer me any advice it would be appreciated,, thanks

If it was an ABC type engine you don't break them in overly rich. Did you check the instructions included with the engine break in procedures are usually listed?

yes i read the manual but it was very vague it just stated that it shouldn't to run overlean. I didin't run it to rich to do any damamge though ,, i don't think anywayz ,, it was only about 1/4 to 1/3 or a turn away from peak rpm

The full throttle part was correct, unfortunately the really rich part is not good, nor was running it non-stop through the first tank. Run it full throttle at a rich TWO stroke setting (near the 2 - 4) break for 3-5 min, then shut down & let it cool. Repeat that process for the first tankfull. Continue the process slightly leaner, but not peaked, for a second tankfull & you should be good to go.

You may have hurt it a bit, but the GMS takes quite a bit of bashing to break it in.

Chris_422
The GMS 47 is an ABC type engine, as such they have a tapered bore, which gives this nip at or near TDC. It is usually an indication that your engine has the correct fit piston to cylinder. It will loosen up a little as the engine runs in more. Just don't be in a hurry to lean it out to quick. Read an follow the instructions that came with the engine.


Cheers.

Thanks for the info, took the engine to the feild today and flew all day with no problems, it ran great and has lot's of power. It's still really tight at TDS , but im sure that will go-away in time and that's usually a good thing for a new engine