Originally Posted by jeffreylin
I tried it step by step but that engine died in the middle of a race--a broken piston. Luckily it was a handout motor ($50 for race entry includes a motor). It wasn't the best motor out there so the failure could've been due to material or worksmanship.
A broken piston probably has very little to do with the break-in method. My name isn't Rody or Cyrul, but I'm guessing the most likely reason for a broken piston is poor materials or possibly over revving.
But looking back, I see a problem. You stated that once the engine is up to temperature, we should richen the top needle until the engine flames out. Well I had to open it so much before it flamed out that the engine cooled down and was only running at about 100F. That couldn't have been good?
If the motor was up to operating temperature and you richened it until it flamed out it shouldn't have dropped that much. Also, he only suggests doing that to flush out the motor. If it was new and clean it probably didn't need to go to the full extreme of flaming out. However, even still it didn't hurt the motor.
Also, as mentioned in other posts before, wouldn't full throttle for 5 tanks especially when the engine is tight and temperature is lower be bad for the con rod? I mean yes replacing it is always a good idea but having to replace a $20-$30 con rod right after breaking in seems a bit excessive doesn't it?
When the motor is above 175F the piston isn't anywhere near as tight as it feels when cool. The reason it's tight when cool is because the sleeve has contracted and is pinching the piston at TDC. This is another reason I try not to rev my motor(s) hard until they have been started a few seconds. I set the hi idle on my radio to start the motor and let it hi idle for 8-10 sec.
I'm sure Josh won't be on here any time soon because of the Reedy so I hope I was able to help a little