Hi All; So at home I have a basic old compression tester with a push in rubber tipped spigot, that has worked great for many years. Wanted to have one here in Arizona as well, so went to Harbor Freight and picked up a nifty kit with several adapters and an extension flex hose. The bike is an '07 RK with 103" bigbore kit, SE 255 cams, stock 85 cc heads, flat top pistons, etc. Allowing .009 for deck clearance, .045 for head gaskets, 1.5 cc for valve clearance, I figure 9.72 SCR and 9.27 CCR using the 255 cam intake closing angle of 25 deg. And this should give a CCP of around 191 psig. (184 psig corrected for altitude) Initial testing of the bike produced 155/160 psig F/R readings using the 18" flex hose and 12 mm plug hole adapter supplied in the tester kit. I was puzzled as to why these readings seemed so low. So today I reran the tests but this time using the short metal offset rubber-tipped adapter, which requires two hands to seal against the pressure. This time I got 185/190 psig F/R readings. Pretty much bang on what I expected all along. (Altitude here is about 1200' ASL) In thinking about this I figure the difference must be the volume of air in the plug adapter and hose. This volume effectively becomes part of the total head "squish" volume because it compresses and expands with every compression stroke. The gauge release valve is located on the base of the gauge itself. So my conclusion is that short test adapters give the most accurate compression results, and longer hose adapters should be avoided unless its the only option. Anyone else out there noticed anything like this?