Quote Originally Posted by pdt View Post
testing the compression has nothing at all to do with how the engines induction system works.
you are only testing the squashed air in the gap between piston and cylinder head in the combustion chamber.

Compression only starts building up once the piston/rings have closed of both the exhaust and the inlet on the way up the stroke.

many builders of engine do a bench test to see about compression when doing mods to cylinder heads.
probably most of the guys on here who the modded stuff do the same with their race engines etc.

its not uncommon to test for compression without inlet manifolds or carbs or exhaust when rebuilding an engine.

The next time you take off your reed housing check it out, and i bet you the compression will be identical to when you put it back on.

obviously you wont believe me, but go check it out or ask the guru's on here.

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well mate you were right about something,i pulled the reeds on the weekend and did a compression test.it pumped 120psi 2 more then without the reeds fitted.same guage.