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GLASS HEAD BRIGGS ENGINE
- Thread starter Crispin
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I've seen a few of these but he hadn't got it running in them.
Looks like he's got far lower compression than the original head from memory. Not surprised he's got interference on his camera with all that is being radiated from the piece of standard wire with no shielding (metal) round the spark.
Sounds like one of the old hit 'n' miss engines.
Sounds like one of the old hit 'n' miss engines.
It's interesting to see it firing, usually were only guessing what's happening in there.
Briggs & Stratton have been making engines for donkeys years and still are I imagine, for mowers and other small appliances.
I had a B&S 12 hp in my ride on mower before I left the U.K.
Briggs & Stratton have been making engines for donkeys years and still are I imagine, for mowers and other small appliances.
I had a B&S 12 hp in my ride on mower before I left the U.K.
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What makes you say that?
I seem to remember them as flat with the sparkplug above the piston. His looks about the same. I did think that TDC looked low. Perhaps a shorter conrod?
The side valve "wastes" a lot of space. Never seen it in situ like that.
Yep, flat head on the 4hp B&S I've worked on too.
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The glass looks to be getting on for 10mm or so from the top of the piston. When you see it disassembled, there is a clear void milled out. The spark electrode enters from the side and is sparking to a post between the cylinder and inlet valve. The post is around 8mm long by the looks of it.
From memory, the head was flat above the piston rising to a recess above the valves which probably gave some swirl as the mixture entered the combustion chamber.
The change to overhead valves of course does away with the wasted space with the side valves and allows far higher compression.
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