Bert,
When rebuilding the fuel system after the 213 flights, the muffler pressure tap was about 80% clogged. The interior of muffler was relatively free of deposits. The tank had a few small carbon floaties. the felt clunk was dirty but not encrusted. No crap trap or vent line filter was used.

Others have reported choking deposits, which leaves me wondering about the comparisons and the question of whether deposits are primarily left by the oil and if so, what might be the comparison between oil based and synthetic. Another is the mix ratio.

I've not used synthetics in this engine and the ratio has been 20:1

What are your thoughts?