Complaint No 1 about Enya Engines is because they are hard to start and break in when NEW. That is true for the Iron Engines like the Enya 15III, Enya 19, Enya 35III, and some of the Schnuerle ones like the Enya SS25/30 and 40.
However, if you apply the steps below you will have a strong, 1st flip, reliable, and long lasting engine in no time!
When the engine is new and it comes extra tight from Enya it will be harder to start (too much resistance to turn) but the harder to get started the better compression and power it will have.
These are the steps I do to break in Enya Iron Engines that have been working very very well for me. All it takes is about an hour and a half of running time.
First Phase – Thermal Treating
I do 10 short runs of 1min with the needle set so the engine burbling between 4/2, letting the engine totally cool between runs. Then 8 short runs of 2 min and 6 of 3min (perhaps the 6x3min is not necessary but I do it anyway)
Second Phase - Unleashing the Power
3 runs of 6 minutes with the same needle setting as in phase 1. Depending on how tight the engine is it may require more runs the same way. Never had to do more then 5 times. I pinch the fuel line with care to make the engine keep at peak rpm for 8 to 10 seconds, then I release the fuel line, wait for about 25s and repeat the process until the end. The top rpm improves significantly in this stage. I call the engine ready to fly when I see that there is no more gain in the peak rpm. At this point as soon as I release the fuel line the rpm returns back immediately to the set rpm.
If you break in just letting the engine run rich and don't peak it out, it will never break-in and develop good power. You will mistakenly think it is a lame engine!
Of course, these steps are not for Ring, ABC or AAC Enya Engines, only for those with Iron P/L.