Farm Engine Compression.

[nowramfg]

This is my Farm Engine from Strictly IC Magazine.

I need to know about the compression that is required to make it run.
The plans call for the piston to stop about 3/8" from the top of the cylinder. I built it like that and it had no noticeable compression.
I then remachined the cylinder so that I reduced the space to about .200". It showed "some" compression.
It has lots of spark, fires at TDC +/- a degree or 2.
Without the spark plug, I can flip it over about 3 rev's, with the spark plug it will only go about 1 1/2 rev's. so there is compression.
I am looking for guidance to get this running.
I would like to add a H&M setup to it also.

 

[cfellows]

I think the 3/8" head space is not the problem. It sounds more like you have a compression leak, either around the valves, past the piston, or around the spark plug. When flipping over by hand, the engine should rock up against the compression, then bounce back. Check out Brian Rupnow's thread on this Kerzel hit n miss build. The subject of compression is covered at great length.

http://www.homemodelenginemachinist.com/index.php?topic=10831.0

Chuck

 

[nowramfg]

Thanks for the reply.
There is no rocking up to compression,& the valves do seal, I think I need to increase the C.R.
I did just read that topic.
The engine only has a 7/8" bore, that is why I figured that the big space was useless.
The piston does not have rings, but if I put my hand over the end of the barrel, the piston will not drop out, and when you push it in, it seals great.
You can feel suction on the intake as you turn it over.
I am sure that this is an Upshur design. I don't have the prints here at work with me.