I have been having problems with my 2.0 aircooled engine since halfway back from our trip to the Outer Banks in August.  I just now had the time to really check into it.  I assumed the worst and was preparing for an engine rebuild, assuming we had burnt a valve, or cracked a head.  The symtom was the engine was only running on three cylinders.  Number four cylinder was not doing anything and its plug was badly fouled out. Installing a new plug had done nothing.
    So before pulling the engine I did a compression check on all the cylinders, hot and cold, wet and dry wet meaning I added 1 tablespoon of oil down the sparkplug hole.

Bently manual compression check values for this engine are taken with a minimum oil temp of 86deg F  
Compression pressure values,      87-131psi

Wear limit bar                               73 psi

Maximum permissible difference 
between all four cylinders                44psi          

#3 120 cold dry                #1 130 cold dry
     125 cold wet                    135 cold wet
     123 hot dry                      125 hot dry
     125 hot wet                      135 hot wet

#4 145 cold dry                #2 145 cold dry
     150 cold wet                    150 cold wet
     130 hot dry                       125 hot dry
     140 hot wet                       140 hot wet

It is definitly not firing on cylinder number four at all.  So we have spark, we have compression, what could be missing???  
    
David White
1982 aircooled Westy

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