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Author Topic: M91 water cooled vertical H&M. A recap.  (Read 291 times)


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Re: M91 water cooled vertical H&M. A recap.
« on: May 23, 2021, 09:23:28 am »
Hi Jack, Nice write up!

I submit to you that if you have it set up that nicely you are able to hand start it from cold. (no rope needed)

I would agree that 200:1 is likely not enough oil. I use MMO at 15 to one which many consider excessive. You might consider trying somewhere in between.

I agree that the 92 and 94 octane tru-fuel is a very good option. I use Coleman in some, tru-fuel in some and 100 LL (aircraft fuel) in some. I like to try them all and note which is best for the engine drinking it. All are mixed with MMO. I use synthetic clock oil on piston skirts and the lower bore or Mobil 1  0W-16 or 0W-20. One more thing. When I have the piston out to shave off enough to reduce the compression, I always put a very small and smooth chamfer on both ends of it.


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