Here is a tool my friend Jack made for testing crankcase seals on the H2's. The same concept will work for the H1's, but of course an adapter would have to be fabricated for the smaller case. The tool was made to test the seals on an assembled case and the rods will fit up into the adapter's sleeve. We've tested all of ours and it works great. Five good cylinders and one bad, really bad. Afterwards we pulled the crank and found a badly worn seal. This saved a lot of guess work and was cheap to make. Just grease the plexiglass sealing surface and hold it down while pumping. If it good, you'll see the vacuum rise and hold at 5~6 lbs.

We wanted to share the idea.
Regards, Gordon