XCOR has demonstrated a working H2 piston engine with sufficient power output to drive a motorcycle.
They stress tested their seals by putting them in a conventional motorcycle engine and driving it cross-country. They didn't put their engine into a motorcycle.
Your correct about the testing of pump parts on the motorcycle, but it was bearings and not seals.
I did some more in depth source for the technology involved with the IVF ACES. The technology is a combination of Boeing and XCOR. Small LH2/LOX thrusters and GH2/GO2 piston engine from Boeing and cryo pumps, a heat driven power takeoff to drive the pumps (exhaust from the GH2/GO2 engine) and a 20-30klbf LH2/LOX main engine from XCOR with unlimited restarts. I believe that XCOR would be the manufacturer for all of the piston devices even those based on Boeing technology since they would all share common parts.
Question is the GH2/GO2 piston engine public or private IP?
This would make an ACES stage an in-space tug reusable until something breaks and has to be repaired. Same tech could be incorporated into a reusable Lunar Lander.
Add a heat sheild for aero-braking for lunar return to LEO and it becomes a very atractive system for LEO to EML-1/2 cargo and crew transport. Just need a LEO cryo depot and possibly a EML-1/2 depot as well for the reusable Lunar Lander.
A stretched tank version of the reusable tug could easily transport prop from the LEO depot to the EML-1/2 depot. This would make the costs of transport of prop to the EML-1/2 depot basicly the cost of the propelant (at LEO prices) used in the tug + 20% ops and profit. If prop at LEO is valued at $3K per kg then the prop at EML-1/2 would be about $7K per kg. Transport costs to get cargo to the Lunar surface from LEO would be about $10-12K per kg. 50mt of cargo delivered to Lunar surface from Earth would be $125M (FH) + $500M (used propelant) or about $625M. The tug and lander operations and profit charges could add another $100M to the price or more realistically about $750M. It would take 2 - 130mt SLS to equal this capability at their cheapest unit price of $700M per launch (5 launches per year) or $1.4B total or at the low flight rate $1B per launch (2 launches per year) or $2B total. ($ values are for comparison and are accurate to about +/-20%).