Killer,


Your engine must be broken-in properly, before you should expect it to idle and run properly.
Please follow [link=http://www.rcuniverse.com/forum/Tapered%2DBore_Engine_Break%2Din_%2D_Upgraded/m_1850473/tm.htm]this RCU thread[/link], for the correct procedure, and see what OS have to say in [link=http://www.osengines.com/faq/product-faq.html#q2]their own Q&A page[/link].

The procedure stated in the 'generically written' manual that you have, is incorrect and has been 'disowned' by the OS 'brass'.


FBD, after the break-in is completed, I cannot agree that a 11x6 prop can be considered 'over-propping' this engine.
In flight, this prop size will fly the model a bit more slowly, but speed loss on vertical and ascending maneuvers is much reduced. Prop braking on steep landing approaches is significantly increased also.

In fact, props as large as 12x7 are deemed suitable for this engine, if the manual and Tower's web page can be trusted on this issue.