I'll ck the retainer when I take it out. RCjapan would be half the cost, but shipping would prob run u around $30. Guy on FG reported same situation but got quite a few hours out of it before it happened.
Thanks for the RC Japan tip. The parts needed (piston, ring, liner, retainer clip) are about 7700 yen which is about 65$. Even if shipping was 30$, I'm still ahead by at least one third. That's significant cost savings. I also priced the Hatori header for the engine. That was an eye opener at less than 10 bucks (compare at 75$ from local source). Ordered that too.
Commissioned one of my spare engines but kept the ignition module. Engine fired right up; back in business and hope to fly today
"Edit" the actual shipping cost was 2190 yen to New Jersey ($18.50). Better than expected; I would use them again ....