Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

With the help of our Gil and a very useful Facetime phone call where we could see each other, see the problem and test fixes. 

Problem seemed to be virtually NO compression.  We checked the exhaust and intake valves which seemed to be working fine having removed the head to observe.  Ended up taking head off, cylinder off and found the single green O ring in the groove closest to the top of the piston was barely making contact with the cylinder walls.  I will order some new O rings, but short term we switched the O ring to the other/lower groove...oiled it well and reassembled.   Using a bit of tape to protect the protruding crankshaft on the side without counterweights...a drill clamped on that side running in reverse got it started.  We were both elated after more than 90 minutes of messing with it.  We had even swapped the head from my M90 to see if it made any difference...answer NO.  Problem was definitely the M91's O ring.

After running it for maybe 15 minutes total with a couple of stops and restarts...it ran quite well AND compression seemed to have been restored...maybe that O ring did not have enough oil to make a proper seal??? 

My thanks to Gil for his time, patience and step by step problem resolution.  Funny, Gil and I have been online and phone friends for many years, but this was our first Facetime call where we got to see each other "in person" (sort of). 

Thanks again Gil,

Rog