Hi twostroker,
There were high and low compression models, however, I can't remember details about what made them high or low compression.
I am pretty sure though, that the high compression models had a
Decompressor Valve coming out of the head. Low compression models don't use these.
If you ever had a high-compression model and the wrong head, someone had blocked off the decompressor valve outlet, or the decompressor was faulty, you'd know because it was damn near impossible to pull start. That wasn't an issue on the lower compression models (When you pull the starter to rotate the engine, because there's less compression on each side of the engine, it isn't as difficult to pull), hence no need for a decompressor valve.
Cheers,
pau13z
