OK I finished breaking in my echo 21cc-here are specs:
echo 21cc srm2100 short block -new
crrc pro 26i replacement cdi ignition-auto advance
crrc pro 26i hall sensor
crrc pro 45 prop hub
custom made adapter for prop hub
stock muffler opened up slightly from exhaust port side and cut open a little on outlet side
stock carb isolator machined down and pulse port channel machined for carb mount copy of fpe1.3
walbro WA 163 carb-9.5mm venturi
running on zenoah 2 stroke oil at 50:1 ratio 93 octaine gas (31 degrees on timing)
Total flying weight less ignition battery includes -eng-ign-muffler-carb-prop-hub = 45 oz
APC 16 x 4W prop best RPM 8300........ I'm a happy camper!!!
or should I not be??
Stock fpe specs are around 43oz and an APC 16 x 8 @ 7450 rpm

Hi Mark

Glad to hear your happy, did the carb isolator and other parts work ok.

Ivy McNeil

With that APC 16x4 prop seems like doing nothing at all to the engine would turn just as good RPM. I am not sure though. Put the APC 16x8 prop and watch the RPM drop. Maybe more break-in is needed. Capt,n

ABSOLUTELY!!! The machining worked out really well.I installed the hub you made at 30-31 degrees of timing or so and have'nt changed it since,it ran just great!!! Hand starts in 2-3 flips after primming it.The carb mount works good too.I originally broke it in with a WA 222 11.1mm carb and when i switched to fuel with less oil I had trouble with it going rich and surging back and forth to lean with the break in prop i had on it-evolution 15 x 6- best was 8000 rpm with an idle of 2200 rpm and changed to a WA with a 9.5mm venturi and an APC 16 x 4W prop best rpm 8300 rpm idle was 1600 rpm - reliable too.Plus the pull with the 16 4 prop felt to be a bit more on the stand i was using than the 15 x 6 prop.and at low idle the prop wash was minimal.I used a formula posted here to come up with the venturi size.I had tried a top flite 15 x 6-10 prop and had only 7000 rpm and too high of an idle- even with proper tunning.I almost don't want to try any thing else oh by the way I gots me a lanier stinger 60 arf to mount it in I know but i figured the fpe with 16 x 8 prop has around 10 - 10.5 lbs thrust and well............I over do stuff, anyways it has a wing of 810 sq in flying wight of around 7 lbs with the .60- .90 engine.