Compression spec on Agility 50 4T?

[eamartin]

Does anyone know the factory spec? 

[Sodster]

Hi
The service manual says 16kg/cm² (228 psi).

[eamartin]

Thanks, Sodster.  I came up with the same 228 psi conversion and thought it awfully high but I'm no mechanic.  My Agility 50 4T is a worn out beater.   After cleaning the head, lapping the valves, installing new valve seals and installing new rings I got a cold reading of 127 psi.  And the scooter runs okay.   I'm just wondering  if I should use this head with a cheap 72cc BBK installation.

[Sodster]

I agree, it sounds rather high. At 127 psi, did it run well? I.e. did it have reasonable power output or was it "tired"?
If valves and rings are ok I'd guess you may have a blown head gasket (it may sometimes be hard to spot) or a warped head. Use a straight ruler on the head to cylinder mating surface with a light shining from behind. Move the ruler around. You should not see any light between ruler and head.
A general rule for increasing engine volume: increase stroke or bore and keeping the head volume intact will increase compression ratio. This may lead to knocking. You will also want to check the geometry of the head volume to control squish and any imperfections that increase risk of knocking.
One way to lower compression ratio, by increasing head volume, is to use a thicker head gasket but it's only advisable if the head is hemispherical. Again check squish.
If the head is straight I'd use it for a BBK. 

[eamartin]

Mine takes off quickly and does 30mph on flat ground.  Seems okay for a beater.  I'm thinking of installing a cheap 72cc cylinder/piston for hills and a little more speed.  If I do, I'll get a new head gasket as part of the package.

[TD46]

Just picked up a 2010 agility with 100 miles on it. Scoot looks like it just came from dealer. Bad news is i got 52 psi compression. So a rebuild it is. Never done one so excited to tear onto it. Should i remove the motor and tear it all the way down? Or leave it in and just do the too end? So many kits out there any advice would be greatly appreciated. Thanks!