Got some Q's about my Stuart 10H

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KennyMcCormick315

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A year or two ago I bought a premachined assembly kit of one of these little gems, and it went together reasonably well. Runs nicely enough, if I put air inside it it spins right up! But it ain't running right. I had ideations of running it off an aquarium pump so I could have it loping over at 40-50RPM pretty much constantly, but it never has been willing to run on such low pressure.

I found it recently, dusted it off, cleaned it out, re-oiled it, and hooked it to a low-end Testors airbrush compressor the other week. Joy of joys, it spun right up like it always did! Just got done recording a video of it:




Any tips on getting it to run better? I know it's got a lot of blow by...Stuart intends you to use steam oil to seal the piston for some reason...and that's not helping it. But it feels like it has 70% more power when the piston's moving towards the crank than it does away, and 95% of the time when it stalls at low RPM it does so at bottom dead center. Logic says it'd be down on power in both directions to an equal degree if blowby was the only issue. Also feels like the timing's a bit off, or perhaps valve stroke?

Also, from day one, if I put any torque whatsoever on the main bolts, it just binds right up. If I snug the nuts down just barely enough to qualify as snug, however, it spins free as can be. Something I can fix without access to a lathe/mill?
 
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